AGREEMENT OF LIMITED PARTNERSHIP

Exhibit 3.6

AGREEMENT OF LIMITED PARTNERSHIP OF

AMERICAN ENTERPRISES MPT HOLDINGS, L.P.

THIS AGREEMENT OF LIMITED PARTNERSHIP, dated as of December 9, 1996 (the “ Agreement ”), is entered into by and between Capital Yield Corp., a Delaware corporation (the “ General Partner ”) and the individuals who are executing this Agreement as Limited Partners (such persons and anyone who in the future may be admitted to the Partnership as a limited partner in accordance with this Agreement are hereafter referred to collectively as the “ Limited Partners ” and individually each as a “ Limited Partner ”).

WITNESSETH :

WHEREAS, a Certificate of Formation (the “ Certificate ”) to form the Partnership has been filed with the Secretary of State of the State of Delaware; and

WHEREAS, the General Partner and the Limited Partners desire to enter into this Agreement to continue the existence of the Partnership and to set forth their agreement as to their rights and obligations with respect to the Partnership;

NOW, THEREFORE, in consideration of the mutual promises herein set forth, the parties hereby agree as follows:

ARTICLE I
DEFINITIONS; FORMALITIES

1.01.    Definitions.

“ Act ” means the Delaware Revised Uniform Limited Partnership Act, as amended.

“ Additional Capital Contributions ” means the amount of any additional capital contributions made by a Partner pursuant to Section 3.01(b)  hereof.

“ Agreement ” means this Agreement of Limited Partnership, as originally executed and as hereafter amended or modified from time to time.

“ Capital Account ” means the capital account determined and maintained for each Partner in the manner provided for in the Tax Allocations Addendum.

“ Capital Contribution ” or “ Capital Contributions ” means the Initial Capital Contribution and any Additional Capital Contributions made by a Partner pursuant to Section 3.01 hereof.

“ Capital Priority Amount ” means, with respect to each Partner, an amount equal to the sum of (i) the Partner’s Net Invested Capital plus (ii) the Partner’s Unrecovered Partner Priority Return at the time of determination.

“ Cash Available for Distribution ” means, with respect to any fiscal period, an amount, determined by the General Partner in its sole and absolute discretion, equal to the cash revenues of the Partnership from all sources (including without limitation any net proceeds received by the Partnership upon the sale or other disposition of Partnership assets other than in the ordinary course of the Partnership’s business, the net proceeds from any refinancing or borrowing by the Partnership, and interest income on Partnership working capital) during such fiscal period plus such reserves that the General Partner determines are no longer necessary to provide for the foreseeable needs of the Partnership, less (i) all cash expenditures of the Partnership during such fiscal period, including, without limitation, operating expenses, debt service, repayment of Partner Advances and interest thereon (which shall be repaid in full prior to any distribution of Cash Available for Distribution), administrative expenses, and expenditures incurred by the Partnership in connection with capital transactions, and (ii) such reserves that the General Partner determines to be necessary or appropriate to provide for the foreseeable needs of the Partnership.

“ Certificate of Limited Partnership ” means the Certificate of Limited Partnership, and any and all amendments thereto, filed on behalf of the Partnership with the Secretary of State of the State of Delaware as required under the Act.

“ Code ” means the Internal Revenue Code of 1986, as amended (or any corresponding provision or provisions of succeeding law).

“ Estimated Market Value ” means the estimated fair market value of the Partnership’s interest in the Operating Partnership as determined by the General Partner taking into account, among other relevant criteria, industry-standard valuation procedures, capitalized earnings and cash flow of the Operating Partnership, sales of comparable companies and such other factors as the General Partner, in its sole and absolute discretion, determines are appropriate, including, without limitation, market conditions at the time the

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Estimated Market Value is to be determined and any discount appropriate for the valuation of such an interest.

“ Fiscal Year ” means the fiscal year of the Partnership, which initially shall end on December 31 of each year.

“ General Partner ” means Capital Yield Corp., a Delaware corporation, in its capacity as general partner of the Partnership and its permitted successors or assigns or any Person admitted as a substitute general partner pursuant to this Agreement.

“ Initial Capital Contribution ” means the amount of the capital contribution made by a Partner as described in Section 3.01(a) .

“ Limited Partners ” means the Persons who execute this Agreement as Limited Partners as of the date hereof and any Person subsequently admitted as a substituted or additional Limited Partner pursuant to this Agreement (including any Limited Partner who becomes a Withdrawn Limited Partner pursuant to Section 5.02(b) ). Reference to a “ Limited Partner ” means one of the Limited Partners.

“ Majority ” means Limited Partners other than Withdrawn Limited Partners, if any, with a majority of the Percentage Interests held by the Limited Partners, excluding any Partnership Interests held by any Withdrawn Limited Partners.

“ Management Limited Partner ” means a Limited Partner who is executing a signature page to this Agreement as a Management Limited Partner as of the date hereof or who later acquires an interest in the Partnership as a Management Limited Partner in accordance with the terms of this Agreement.

“ Net Invested Capital ” means, as to each Partner, the amount of such Partner’s Initial Capital Contributions, increased by the amount of any Additional Capital Contributions made by such Partner after the date of this Agreement pursuant to Section 3.01(b) , and reduced, as and when made, by the amount of cumulative distributions to such Partner pursuant to Section 3.04(a)(i)  which, pursuant to Section 3.04(b) , are applied to reduce such Partner’s Net Invested Capital.

“ Net Profits ” or “ Net Losses ” means, with respect to a fiscal period, the net profits or net losses of the Partnership for Federal income tax purposes during such period as determined under section 702 of the Code.

“ Operating Partnership ” means American Enterprises MPT, L.P., a Delaware limited partnership, and any successor entity.

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“ Partners ” means the General Partner and the Limited Partners. Reference to a “Partner” means any one of the Partners.

“ Partner Advances ” means loans or advances, if any, made by a Partner to the Partnership from time to time pursuant to Section 3.01(b) .

“ Partner Priority Return ” means an amount, computed as of the end of each calendar month with respect to each Partner, equal to the product of (i) the quotient of the Prime Rate in effect for such month plus one-quarter of one percentage point divided by twelve (12), multiplied by (ii) the sum of (A) the average daily outstanding Net Invested Capital of the Partner during such month plus (B) the average daily outstanding Unrecovered Partner Priority Return for such Partner during such month. To the extent that the Partner Priority Return is not paid to a Partner with respect to any month, such unpaid Partner Priority Return shall be added to the Unrecovered Partner Priority Return and shall itself be subject to the Partner Priority Return thereafter. The Partner Priority Return shall begin to accrue with respect to a Partner as of the first calendar month in which the Partner makes Capital Contributions to the Partnership.

“ Partnership ” means the limited partnership formed under the Act by this Agreement by the parties hereto, as said Partnership may from time to time be constituted.

“ Partnership Interest ” means the entire interest of a Partner in the Partnership at any particular time, including the right of such Partner to any and all rights and benefits to which a Partner may be entitled as provided in this Agreement, together with the obligations of such Partner to comply with all the terms and provisions of this Agreement.

“ Percentage Interest ” means the percentage ownership interest of a Partner determined in accordance with this Agreement.

“ Person ” means any individual, partnership, corporation, trust, or other legal entity.

“ Prime Rate ” means for any period the daily average of the “base rate” for corporate loans at NationsBank, N.A. or such other large U.S. money center banks as shall be designated from time to time by the General Partner.

“ Prior Profit Amount ” means the amount computed by the General Partner, in its sole and absolute discretion, each time that one or more new Partners are to be admitted to the Partnership pursuant to Section 4.01(c)  or the Partnership Interest of a Management Limited Partner is converted to that

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of a Withdrawn Limited Partner in accordance with Section 5.02(b) , that a Partner would receive under Sections 3.04(a)(iii)  and 3.04(a)(iv)  if the Partnership were to sell all of its assets for cash equal to the Estimated Market Value as of the Valuation Date with respect to such admission or conversion and were to distribute the estimated net proceeds of such deemed sale, after payment of all Partnership liabilities and the allocation of any Net Profit or Net Loss of the Partnership for the fiscal year of such deemed sale (including for this purpose the estimated gain or loss that the Partnership would realize on the deemed sale), to the Partners (other than the new Partners then being admitted) pursuant to Section 3.04(a) . In the event new Partners are admitted to the Partnership or the Partnership Interests of Management Limited Partners are so converted on more than one date, Prior Profit Amounts shall be calculated and credited to the Partners for each such admission or conversion, so that any appreciation in the Estimated Market Value of the Partnership during the period between Valuation Dates will be credited solely to those Persons who are Partners during such period. The General Partner shall be authorized and directed to make such adjustments to the computation of Prior Profit Amounts and the manner in which distributions and allocations are made to the Partners with respect to such Prior Profit Amounts as the General Partner determines are necessary or appropriate to insure that any appreciation in the Estimated Market Value of the Partnership is properly credited to those persons who are Partners (other than as Withdrawn Limited Partners) during the period in which such appreciation occurs.

“ Subscription Agreement ” means the Subscription Agreement being executed and delivered to the Partnership by each initial Limited Partner, other than Mitchell and Steven Rales, in connection with his or her acquisition of a Partnership Interest.

“ Tax Allocations Addendum ” means Exhibit A to this Agreement as it may be amended from time to time in accordance with Section 3.07 .

“ Tax Matters Partner ” means the General Partner.

“ Unrecovered Partner Priority Return ” means, with respect to each Partner, such Partner’s cumulative Partner Priority Return reduced, as and when made, by the amount of all previous distributions made to the Partner pursuant to Section 3.04(a)(i), which pursuant to Section 3.04(b)  were applied to reduce such Partner’s Unrecovered Partner Priority Return.

“ Undistributed Prior Profit Amount ” means, with respect to each Partner, the Prior Profit Amount credited to such Partner pursuant to Section 4.01(c)  reduced, as and when made, by the amount of all distributions to the Partner pursuant to Section 3.04(a)(ii)  with respect to such Prior Profit Amount. In the event new Partners are admitted or Management Limited

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Partners become Withdrawn Limited Partners on more than one date and as a result there are Prior Profit Amounts credited to the Partners with respect to more than one Valuation Date, the Partnership shall separately account for the Undistributed Prior Profit Amounts with respect to each such Prior Profit Amount.

“ Valuation Date ” means (i) the date immediately prior to the date of the admission of one or more new Partners pursuant to Section 4.01(c) , or (ii) the effective date on which a Management Limited Partner becomes a Withdrawn Limited Partner in accordance with Section 5.02(b) .

“ Withdrawn Limited Partner ” means any Management Limited Partner whose Partnership Interest has been converted into that of a Withdrawn Limited Partner pursuant to Section 5.02(b) .

1.02.    Continuation of Partnership; Certificate of Limited Partnership .  The General Partner formed the Partnership on November 21, 1996, pursuant to the provisions of the Act. The Partners hereby execute this Agreement for the purpose of continuing the existence of the Partnership and setting forth the rights, duties and relationship of the Partners. If the laws of any jurisdiction in which the Partnership transacts business so require, the General Partner also shall file, with the appropriate office in that jurisdiction, a copy of the Certificate of Limited Partnership as filed with the office of the Secretary of State of the State of Delaware or any other documents necessary for the Partnership to qualify to transact business and to establish and maintain the Limited Partners’ limited liability under the Act. The Partners further agree and obligate themselves to execute, acknowledge, and cause to be filed for record, in the place or places and manner prescribed by law, any amendments to the Certificate of Limited Partnership as may be required, either by the Act, by the laws of a jurisdiction in which the Partnership transacts business, or by this Agreement, to reflect changes in the information contained therein or otherwise to comply with the requirements of law for the continuation, preservation, and operation of the Partnership as a limited partnership under the Act.

1.03.    Name .  The name of the Partnership is American Enterprises MPT Holdings, L.P..

1.04.    Names of Partners .  The names of the partners of the Partnership as of the date of this Agreement are set forth on the signature pages of this Agreement.

1.05.    Principal Place of Business .  The principal place of business and the principal office of the Partnership shall be located at 9211 Forest Hill Avenue, Suite 109, Richmond, Virginia 23235. The Partnership may have such

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other or additional offices, either within or without the State of Delaware, as the General Partner shall deem advisable.

1.06.    Registered Agent  The name and address of the initial registered agent of the Partnership shall be Corporation Service Company, 1013 Centre Road, Wilmington, Delaware 19805. The General Partner may change the registered agent from time to time, in its sole and absolute discretion.

1.07.    Term .  The term of the Partnership commenced on October 15, 1996 and shall continue until the Partnership is dissolved in accordance with the provisions of this Agreement.

1.08.    Title to Partnership Property .  Legal title to the property of the Partnership shall be in the name of the Partnership.

ARTICLE II
BUSINESS OF THE PARTNERSHIP

2.01.    Purposes .  The purposes for which the Partnership is formed and the businesses to be carried on and promoted by it are:

(a)                to invest in, and acquire, hold, deal with and dispose of an interest in, the Operating Partnership, including without limitation exercising any rights of a limited partner in the Operating Partnership; and

(b)               to engage in any one or more businesses or transactions, or to acquire all or any portion of any entity engaged in any one or more businesses or transactions which the General Partner, in its sole and absolute discretion, may from time to time authorize or approve, whether or not related to the business described in Section 2.01(a)  or to any other business then engaged in by the Partnership.

2.02.    Authority .  In order to carry out its purposes, the Partnership is empowered and authorized to do any and all acts and things necessary, appropriate, proper, advisable, desirable, incidental to or convenient for the furtherance and accomplishment of its purpose and for the protection and benefit of the Partnership, including but not limited to the following:

(a)                buy, own, operate, assign, mortgage, or lease any property;

(b)               enter into any kind of activity, and perform and carry out contracts of any kind necessary to, in connection with, incidental to, or desirable to, the accomplishment of the purposes of the Partnership;

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(c)                borrow money and issue evidences of indebtedness in furtherance of the Partnership business and secure any such indebtedness by mortgage, pledge, or other lien; and

(d)               do any and all other acts and things necessary or desirable in furtherance of the Partnership’s business.

ARTICLE III
CAPITAL CONTRIBUTIONS,
PERCENTAGE INTERESTS,
DISTRIBUTIONS AND ALLOCATIONS

3.01.    Capital Contributions; Advances .

(a)              Each Limited Partner shall make an Initial Capital Contribution to the Partnership in the amount set forth in its Subscription Agreement. The General Partner shall make an Initial Capital Contribution to the Partnership in an amount equal to 1.01% of the aggregate Initial Capital Contributions of the Limited Partners.

(b)             In the event the Partnership requires funds in excess of the Partners’ Initial Capital Contributions, the General Partner, in its sole discretion, from time to time may request (but may not require) the Partners to make Additional Capital Contributions to the Partnership, subject to the following sentence; provided, however, that the General Partner shall be required to make Additional Capital Contributions such that the total amount of its Capital Contributions to the Partnership at all times shall be equal to at least 1.01% of the aggregate amount of Capital Contributions made to the Partnership by the Limited Partners. Unless otherwise agreed by all Partners other than any Withdrawn Limited Partners, all Partners other than any Withdrawn Limited Partners shall be offered the opportunity (but shall have no obligation) to make their pro rata shares of such Additional Capital Contributions in proportion to their respective Percentage Interests at the time. In the event one or more of such Partners elect not to make all of the Additional Capital Contribution that it is eligible to make, the other Partners (other than any Withdrawn Limited Partners) may elect to contribute such amounts. The Partners’ Percentage Interests shall not be adjusted as a result of any Additional Capital Contributions. In the event the General Partner, in its sole and absolute discretion, determines it would be more appropriate to obtain all or any portion of the funds needed by the Partnership in the form of loans from one or more of the Partners, the General Partner may request one or more of the Partners to loan or advance such funds to the Partnership, with interest on such loans or advances to be at the Prime Rate plus one-quarter of one percentage point (“ Partner

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Advances ”).  It is expressly understood and agreed that the General Partner may permit one or more Partners to make Partner Advances without also offering the other Partners an opportunity to make Partner Advances, and the Partners shall have no right to make any Partner Advances on a proportionate or other basis except as determined by the General Partner, in its sole discretion.

(c)              Except as provided in Section 5.02(c) , no Partner shall have the right to demand the return of its Capital Contributions or Net Invested Capital prior to the dissolution and liquidation of the Partnership.

3.02.    Percentage Interests . The Percentage Interest of the General Partner at all times shall be one percent (1.00%). The Percentage Interests of the Limited Partners as of the date of this Agreement are set forth in their respective Subscription Agreements. The Percentage Interests of the Limited Partners shall be adjusted from time to time to reflect the admission of any new Partners to the Partnership pursuant to Section 4.01(c) , the withdrawal of any Partner, or the conversion of the Partnership Interest of a Management Limited Partner to that of a Withdrawn Limited Partner pursuant to Section 5.02(b) , and the Partners hereby consent to any such adjustment.

3.03.    Capital Accounts .  The Partnership shall keep a separate Capital Account for each Partner which shall be determined and maintained in the manner provided for in the Tax Allocations Addendum attached hereto as Exhibit A .

3.04.    Distributions .

(a)              The Partnership shall make distributions to the Partners of any Cash Available for Distribution from time to time as determined by the General Partner, in its sole and absolute discretion. Any such distributions, and any distributions to be made to the Partners in connection with the liquidation of the Partnership, shall be made in accordance with the following priorities:

(i)                 first, in the event the Capital Priority Amounts with respect to any Partners are greater than zero, to such Partners to the extent of and in proportion to their respective Capital Priority Amounts, until such amounts are reduced to zero;

(ii)              second, in the event the Undistributed Prior Profit Amounts with respect to any Partners are greater than zero, to such Partners to the extent of and in proportion to their respective Undistributed Prior Profit Amounts, until such amounts are reduced to zero; provided, however, that if there are Undistributed Prior Profit Amounts attributable to more than one Valuation Date and the

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amount to be distributed hereunder is less than the aggregate Undistributed Prior Profit Amounts, then the distribution hereunder shall be made in the order that such Undistributed Prior Profit Amounts arose, so that the Undistributed Prior Profit Amounts from the earliest Valuation Date shall be reduced to zero before distributions are made with respect to Undistributed Prior Profit Amounts attributable to subsequent Valuation Dates, and so on;

(iii)           third, to the Partners, to the extent of and in proportion to the remaining positive balances in their Capital Accounts; and

(iv)          thereafter, to the Partners other than any Withdrawn Limited Partners, pro rata in proportion to their respective Percentage Interests.

Notwithstanding the foregoing provisions of this Section 3.04(a) , the General Partner shall cause the Partnership to distribute to each Partner, without regard to the priorities set forth above, an amount of the Partnership’s Cash Available for Distribution (to the extent thereof) equal to the product of (x) forty percent (40%) multiplied by (y) the Partnership’s estimated net taxable income allocable to such Partner for such period, as determined by the General Partner in consultation with the accountants who prepare the Partnership’s federal partnership information return (Form 1065) for such period, in proportion to the estimated amount of such net taxable income allocable to each Partner, and the amount so distributed to each Partner (the “Tax Distribution Amount”) shall be treated as having been received pursuant to the appropriate provisions set forth above for all purposes of this Agreement, including the determination of the Partner’s Capital Priority Amount, and Undistributed Prior Profit Amounts, as the case may be. In the event any distributions are made pursuant to the preceding sentence and, as a result, any Partners receive distributions in amounts less than the amounts they would have received without giving effect to the preceding sentence, then distributions for subsequent periods pursuant to this  Section 3.04(a)  shall be made on a priority basis so as to cause such Partners to receive, as quickly as possible, the amount of distributions they would have received had the distributions required by the preceding sentence not occurred, subject always to the requirements under the preceding sentence with respect to the distribution of Tax Distribution Amounts for such subsequent periods.

(b)             Any amount distributed pursuant to Section 3.04(a)(i)  (or deemed distributed pursuant to such section) shall be applied first to reduce each Partner’s outstanding Unrecovered Partner Priority Return and after each Partner’s Unrecovered Partner Priority Return is reduced to zero, then to reduce each Partner’s Net Invested Capital.

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3.05.    Allocation of Profits and Losses .

(a)              Subject to Section 4 of the Tax Allocations Addendum, Net Profits shall be allocated with respect to any Fiscal Year in the following order of priority:

(i)                 first, to all Partners whose Capital Accounts have negative balances, in the ratio of such negative balances until such negative balances are brought to zero;

(ii)              second, to the Partners to the extent of, and in proportion to, the amounts necessary to bring the Capital Account balance of each Partner to an amount equal to such Partner’s Capital Priority Amount (prior to giving effect to any distributions made or to be made pursuant to Section 3.04(a)(i)  with respect to such Fiscal Year);

(iii)           third, to the Partners to the extent of, and in proportion to, the amounts necessary to bring the Capital Account balance of each Partner to an amount equal to the sum of (A) such Partner’s Capital Priority Amount plus (B) such Partner’s Undistributed Prior Profit Amount (prior to giving effect to any distributions made or to be made pursuant to Section 3.04(a)(i)  or Section 3.04(a)(ii)  with respect to such Fiscal Year); and

(iv)          thereafter, any remaining Net Profits and gain shall be allocated to the Partners other than any Withdrawn Limited Partners first, so as to cause, as quickly as possible, any positive balances in the Partners’ Capital Accounts in excess of the sum of (A) their respective Capital Priority Amounts plus (B) their respective Undistributed Prior Profit Amounts (prior to giving effect to any distributions made or to be made pursuant to Section 3.04(a)(i)  or Section 3.04(a)(ii)  with respect to such Fiscal Year) to bear the same ratio to each other as the ratio of their respective Percentage Interests bear to each other and second, in proportion to their respective Percentage Interests.

(b)             Subject to Section 4 of the Tax Allocations Addendum, any Net Losses shall be allocated to the Partners as follows:

(i)                 first, to the Partners with Capital Account balances in excess of the sum of (A) their respective Capital Priority Amounts plus (B) their respective Undistributed Prior Profit Amounts, to the extent of and in proportion to such excess amounts until such excess amounts have been eliminated;

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(ii)              second, to the Partners with Capital Account balances in excess of their respective Capital Priority Amounts, to the extent of and in proportion to such excess amounts until such excess amounts have been eliminated;

(iii)           third, to the Partners (if any) with remaining positive Capital Account balances, to the extent of and in proportion to the amount of such balances until such balances have been reduced to zero; and

(iv)          thereafter, to the Partners, in proportion to their respective Percentage Interests.

3.06.     Partnership Funds .  All funds of the Partnership shall be deposited in such bank accounts as shall be designated by the General Partner and all withdrawals from such bank accounts shall be made by checks or other instruments signed by the designated representatives of the General Partner or such other Person or Persons as the General Partner may designate.

3.07.     Tax Matters .

(a)              The General Partner shall be the “ Tax Matters Partner ” for purposes of Code sections 6221 through 6232, inclusive. As the Tax Matters Partner, the General Partner shall prepare and file all required income tax returns and shall manage administrative tax proceedings conducted at the Partnership level by the Internal Revenue Service with respect to Partnership matters.

(b)             The Tax Allocations Addendum sha