Form of Lock-Up Agreement (5% or greater stockholder)

Exhibit 10.3

Form of Lock-Up Agreement – ClearSign Technologies Corporation (clirSPV, LLC)

Public Ventures, LLC

14135 Midway Road, Suite G150

Addison, TX 75001

Ladies and Gentlemen:

The undersigned understands that Public Ventures, LLC (the “Underwriter”) proposes to enter into an Underwriting Agreement (the “Underwriting Agreement”) with ClearSign Technologies Corporation, a Delaware corporation (the “Company”), providing for the public offering (the “Public Offering”) of common stock, par value $0.0001 per share (the “Common Stock”), and warrants, each warrant to purchase Common Stock (the “Warrants,” and together with the Common Stock, the “Securities”).

To induce the Underwriter to continue its efforts in connection with the Public Offering, the undersigned hereby agrees that, without the prior written consent of the Underwriter, the undersigned will not, during the period commencing on the date of the Underwriting Agreement and ending on December 31, 2024 (the “Lock-Up Period”), (1) offer, pledge, sell, contract to sell, grant, lend, or otherwise transfer or dispose of, directly or indirectly, any Common Stock or any securities convertible into or exercisable or exchangeable for Common Stock, whether now owned or hereafter acquired by the undersigned or with respect to which the undersigned has or hereafter acquires the power of disposition (collectively, the “Lock-Up Securities”); (2) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of the Lock-Up Securities, whether any such transaction described in clause (1) or (2) above is to be settled by delivery of the Lock-Up Securities, in cash or otherwise; (3) make any demand for or exercise any right with respect to the registration of any Lock-Up Securities, except as set forth in any agreements with the Company prior to the date hereof; or (4) publicly disclose the intention to make any offer, sale, pledge or disposition, or to enter into any transaction, swap, hedge or other arrangement relating to any Lock-Up Securities. Notwithstanding the foregoing, and subject to the conditions below, the undersigned may transfer Lock-Up Securities without the prior written consent of the Underwriter in connection with (a) transactions relating to Lock-Up Securities acquired in open market transactions after the completion of the Public Offering; provided that no filing under Section 16(a) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), shall be required or shall be voluntarily made in connection with subsequent sales of Lock-Up Securities acquired in such open market transactions; (b) transfers of Lock-Up Securities (i) as a bona fide gift, by will or intestacy, (ii) by operation of law, such as pursuant to a qualified domestic order or as required by a divorce settlement, or (iii) to a family member or trust for the benefit of a family member (for purposes of this lock-up agreement, “family member” means any relationship by blood, marriage or adoption, not more remote than first cousin); (c) transfers of Lock-Up Securities to a charity or educational institution; or (d) if the undersigned, directly or indirectly, controls a corporation, partnership, limited liability company or other business entity, any transfers of Lock-Up Securities to any shareholder, partner or member of, or owner of similar equity interests in, the undersigned, as the case may be; provided that in the case of any transfer pursuant to the foregoing clauses (b), (c) or (d), (i) any such transfer shall not involve a disposition for value, (ii) each transferee shall sign and deliver to the Underwriter a lock-up agreement substantially in the form of this lock-up agreement and (iii) no filing under Section 16(a) of the Exchange Act shall be required or shall be voluntarily made. The undersigned also agrees and consents to the entry of stop transfer instructions with the Company’s transfer agent and registrar against the transfer of the undersigned’s Lock-Up Securities except in compliance with this lock-up agreement.

Notwithstanding the restrictions of the immediately preceding paragraph hereof, during the Lock-up Period clirSPV will be permitted to sell in the public market only, shares of Common Stock that it owns over which it has dispositive power, as long as the net per share price at which the shares of Common Stock are sold exceeds two times the per share price in the Public Offering and the aggregate number of shares of Common Stock sold per day does not exceed 15% of the daily volume of the shares of Common Stock on that date.

The undersigned agrees that the foregoing restrictions shall be equally applicable to any Securities that the undersigned may purchase in the Public Offering.

No provision in this lock-up agreement shall be deemed to restrict or prohibit the exercise, exchange or conversion by the undersigned of any securities exercisable or exchangeable for or convertible into Common Stock, as applicable; provided that the undersigned does not transfer the Common Stock acquired on such exercise, exchange or conversion during the Lock-Up Period, unless otherwise permitted pursuant to the terms of this lock-up agreement. In addition, no provision herein shall be deemed to restrict or prohibit the entry into or modification of a so-called “10b5-1” plan at any time (other than the entry into or modification of such a plan in such a manner as to cause the sale of any Lock-Up Securities within the Lock-Up Period) or a sale of 100% of the Company’s outstanding Common Stock in connection with a merger or corporate reorganization or acquisition of all the assets of the Company (other tthant for redomestication) where the Company is not the surviving entity.

The undersigned understands that the Company and the Underwriter are relying upon this lock-up agreement in proceeding toward consummation of the Public Offering. The undersigned further understands that the lock up provisions of this lock-up agreement is irrevocable and, excluding the third paragraph hereof, shall be binding upon the undersigned’s heirs, legal successors and assigns.

The undersigned understands that, if the Underwriting Agreement is not executed by July 30, 2024, or if the Underwriting Agreement (other than the provisions thereof which survive termination) shall terminate or be terminated prior to payment for and delivery of the Securities to be sold thereunder, then this lock-up agreement shall be void and of no further force or effect.

Whether or not the Public Offering actually occurs depends on a number of factors, including market conditions. Any Public Offering will only be made pursuant to an Underwriting Agreement, the terms of which are subject to negotiation between the Company and the Underwriter.