Under the Securities Exchange Act of 1934
(Amendment No. n/a)*

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Name, Address and Telephone Number of Person
Authorized to Receive Notices and Communications)

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.12d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box o.

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits.  See § 240.13d-7 for other parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

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Statement on Schedule 13D

This Statement on Schedule 13D (this “Statement”) relates to the beneficial ownership of common stock, par value $0.01 per share (the “Common Stock”), of TriMas Corporation, a Delaware corporation (the “Issuer”).  This Statement on Schedule 13D is being filed on behalf of the Reporting Persons (as defined below).

The Reporting Persons are filing this Statement to amend, restate and replace the statements on Schedule 13G with respect to the Common Stock filed with the Securities and Exchange Commission on February 14, 2008 pursuant to Rule 13d-1(d).

This Statement is being filed by the Reporting Persons solely as a result of (i) the adoption of the Rule 10b5-1 Purchase Plan (as defined below) by the Purchasing Parties (as defined below); and (ii) the addition of HIP Side-by-Side I-A, L.L.C., as a Reporting Person.

The additional information required to be included with respect to each Reporting Person is included in the table below:

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HIP is the managing member of TIF I and MIF I.  Associates is the managing member of TIF II, MIF II and HIP Side-by-Side I-A, and is the general partner of HIP and HIP Side-by-Side.  Daniel P. Tredwell is the sole managing member of Associates.

The principal business and office address of each of the Reporting Persons and Daniel P. Tredwell is 177 Broad Street, 10th Floor, Stamford, Connecticut 06901.

The principal business of each of the Reporting Persons is to focus on investments in industrial companies.  Daniel P. Tredwell’s principal occupation is Senior Managing Director of HIP.  Daniel P. Tredwell is a citizen of the United States of America.

During the last five years, none of the Reporting Persons or Daniel P. Tredwell has been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or has been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

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Signature

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated:  March 18, 2009

HEARTLAND INDUSTRIAL ASSOCIATES, L.L.C.

HEARTLAND INDUSTRIAL PARTNERS, L.P.

By:  Heartland Industrial Associates, L.L.C., its General Partner

TRIMAS INVESTMENT FUND I, L.L.C.

By:  Heartland Industrial Associates, L.L.C., the General Partner of Heartland Industrial Partners, L.P., its Managing Member

METALDYNE INVESTMENT FUND I, L.L.C.

By:  Heartland Industrial Associates, L.L.C., the General Partner of Heartland Industrial Partners, L.P., its Managing Member

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HIP SIDE-BY-SIDE PARTNERS, L.P.

By:  Heartland Industrial Associates, L.L.C., its General Partner

TRIMAS INVESTMENT FUND II, L.L.C.

By:  Heartland Industrial Associates, L.L.C., its Managing Member

METALDYNE INVESTMENT FUND II, L.L.C.

By:  Heartland Industrial Associates, L.L.C., its Managing Member

HIP SIDE-BY-SIDE I-A, L.L.C.

By:  Heartland Industrial Associates, L.L.C., its Managing Member

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INDEX TO EXHIBITS

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Exhibit 99.A

EXHIBIT A

JOINT FILING AGREEMENT

Pursuant to Rule 13d-1(k)(1)(iii), we the undersigned agree that the Schedule 13D, to which this Joint Filing Agreement is attached as Exhibit A, is filed on behalf of each of us.

Dated:  March 18, 2009

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Exhibit 99.B

EXHIBIT B

RULE 10b5-1 PURCHASE INSTRUCTION

Instruction, dated March 17, 2009 (this “Instruction”), between each of the entities listed on the signature pages hereto (each, a “Purchaser”) and Credit Suisse Securities (USA) LLC ( “Broker”).  This Instruction was established by each Purchaser to qualify for the affirmative defense and safe harbor provided by Rule 10b5-1 (“Rule 10b5-1”) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”).  The obligations of the Purchasers under this Instruction are several and not joint, and each reference to “Purchaser” hereunder shall be deemed to refer to a specific Purchaser.

WHEREAS, Purchaser desires to purchase Common Shares (“Shares”) of TriMas Corporation (the “Issuer”), par value $0.01 per share (ticker symbol: TRS); and

WHEREAS, Purchaser desires to appoint Broker to purchase Shares on its behalf in accordance with this Instruction;

NOW, THEREFORE, in consideration of the mutual agreements set forth herein, Purchaser and Broker hereby agree as follows:

1.             Subject to paragraph 2 below, Broker shall purchase Shares on each day on which the New York Stock Exchange (the “Exchange”) is open for trading and the Shares trade regular way on the Exchange, at the then prevailing market prices, commencing on the date specified in Section 2; provided, however, that Broker shall continue purchasing Shares in accordance with Annex A hereto up to an aggregate maximum number for all Purchasers of 1,760,000 or 3,000,000 Shares, as determined as set forth on Annex A (as such share amounts are subject to adjustment for stock splits, reverse splits, stock dividends, share combinations and the like) (the applicable maximum number, the “Maximum Number”).  The Share purchases by the Broker pursuant to this Instruction shall be allocated among the several Purchasers in compliance with the sharing ratios described on Annex A.  Purchaser shall pay to Broker the per Share commission set forth on Annex A for each Share so purchased.  Subject to the procedures on Annex A, Broker will execute all transactions in accordance with this Instruction in compliance with ordinary principles of best execution and notify Purchaser of all such transactions pursuant to customary trade confirmations, which shall be provided via email within 24 hours of each transaction.

2.             Notwithstanding anything to the contrary herein, this Instruction shall become effective on the later of (a) the tenth (10th) day after the date hereof and (b) the date on which Purchaser notifies Broker in writing that the Issuer’s Board of Directors has approved the transactions contemplated by this Instruction pursuant to Section 203 of the Delaware General Corporation Law, and shall end on the earliest to occur of the following dates (such date, subject to earlier termination pursuant to paragraph 14, the “End Date”): (i) the date on which the aggregate number of Shares purchased by Broker in accordance with this Instruction equals the Maximum Number specified in Annex A, respectively; (ii) the date on which Purchaser or any other person publicly announces a tender or exchange offer with respect to the Shares; (iii) the date of public announcement of a merger, acquisition, reorganization, recapitalization or comparable transaction affecting the securities of Issuer as a result of which the Shares are to be exchanged or converted into other securities or property; and (iv) the date on which Broker receives notice of the liquidation or dissolution of Purchaser or Issuer, or that Purchaser or Issuer has filed a petition for bankruptcy or reorganization, or a petition for bankruptcy has been filed against Purchaser or Issuer and has not been dismissed within sixty (60) calendar days of its filing.  If Broker determines that any event specified in (i) through (iv) above has occurred, Broker shall promptly notify Purchaser of such fact.

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3.             Intentionally omitted

4.             Purchaser represents and warrants that the purchase of Shares pursuant to this Instruction (i) has been duly authorized by Purchaser, (ii) has been notified to the Issuer’s board of directors, and  (iii) is not, to Purchaser’s knowledge, prohibited or restricted by any legal, regulatory or contractual restriction or undertaking binding on Purchaser.  Purchaser shall immediately notify Broker if it becomes aware of a legal, regulatory or contractual restriction or undertaking that would prevent Broker from making purchases pursuant to this Instruction, and, in such a case, Purchaser and Broker shall cooperate to amend or otherwise revise this Instruction to take account of such legal, regulatory or contractual restriction or undertaking (provided that neither party shall be required to take any action that would be inconsistent with the requirements of Rule 10b5-1(c)).  Until the End Date, Purchaser shall conduct open market purchases of the Shares only through Broker.

5.             Broker and Purchaser acknowledge and agree that Purchaser shall, within two (2) business days after the date of this Instruction, file a notification on either an amendment to an existing Schedule 13G or a new Schedule 13D, in each case relating to Purchaser’s beneficial ownership of Common Shares with the United States Securities and Exchange Commission.

6.             (i)            Purchaser understands that Broker may not be able to effect a purchase due to a market disruption or a legal, regulatory or contractual restriction applicable to Broker.  If any purchase cannot be executed as required by paragraph 1, due to a market disruption, or a legal, regulatory or contractual restriction applicable to Broker, Broker agrees to effect such purchase as promptly as practical after the cessation or termination of such market disruption, applicable restriction or other event.

(ii)           Notwithstanding anything to the contrary herein, this Instruction shall be suspended and the Broker shall not be required to purchase Shares in accordance herewith for such period as required to ensure compliance by the Purchaser or the Broker with the provisions of Regulation M under the Exchange Act in the event of distribution by the Issuer or the Purchaser of Common Shares, Shares or securities convertible to such Common Shares or Shares.

7.             Purchaser represents and warrants that it is not aware of material, nonpublic information concerning the Issuer or the Shares and is entering into this Instruction in good faith and not as part of a plan or scheme to evade the prohibitions of Rule 10b5-1 or other United States federal securities laws.  Purchaser will not, while this Instruction remains in effect, alter or deviate from the terms of this Instruction or enter into or alter any corresponding or hedging transaction or position with respect to the Shares until the End Date.

8.             It is the intent of the parties that this Instruction comply with the requirements of Rule 10b5-1(c)(1)(i)(B) and this Instruction shall be interpreted to comply with the requirements of Rule 10b5-1(c).

9.             Purchaser understands and agrees that, while the Credit Suisse Monetization Services Group is executing purchases of the Shares on behalf of Purchaser pursuant to this Instruction, other desks at Broker that are not participating in such purchases may continue to make a market in the Shares or otherwise trade the Shares for Broker’s own account or to facilitate customer transactions.

10.           From the date hereof until the End Date or termination of this Instruction pursuant to paragraph 14, Purchaser agrees not to discuss with Broker the Issuer’s business, operations or prospects or any other information likely to be related to the value of the Shares; provided, however, that Purchaser

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may communicate with Broker personnel who are not responsible for, and have no ability to influence, the execution of this Instruction.

11.           Broker represents and warrants to Purchaser that it has implemented reasonable policies and procedures, taking into consideration the nature of Broker’s business, to ensure that individuals making investment decisions will not violate the laws prohibiting trading on the basis of material, nonpublic information.  These policies and procedures include those that restrict any purchase or sale, or the causing of any purchase or sale, of any security as to which Broker has material, nonpublic information, as well as those that prevent such individuals from becoming aware of or being in possession of material, nonpublic information.

12.           Purchaser has consulted with its own advisor as to the legal, tax, business, financial and related aspects of, and has not relied upon Broker or any person affiliated with Broker in connection with, Purchaser’s adoption of this Instruction.  Purchaser acknowledges that Broker is not acting as a fiduciary or an advisor for Purchaser.

13.           This Instruction (including Annex A) constitutes the entire agreement between Broker and Purchaser with respect to the subject matter hereof, and supersedes any previous or contemporaneous agreements, understandings, proposals or promises with respect thereto, whether written or oral.

14.           Broker acknowledges that Purchaser may terminate this Instruction at any time by giving notice to Broker.

15.           This Instruction shall be governed by and construed in accordance with the laws of the State of New York and may be modified or amended only by a writing signed by the parties hereto.

16.           This Instruction may be signed in any number of counterparts, each of which shall be an original, with the same effect as if the signatures thereto and hereto were upon the same instrument.

17.           If any provision of this Instruction is or becomes inconsistent with any applicable present or future law, rule or regulation, that provision will be deemed modified or, if necessary, rescinded in order to comply with the relevant law, rule and regulation.  All other provisions of this Instruction will continue and remain in full force and effect.

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IN WITNESS WHEREOF, the undersigned have signed this Instruction as of the date first written above.

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