For bills payable to order, various methods are used in order to ensure the payment. Within these methods, each of which results in a different legal outcome, primary ones are the Aval and Guarantee endorsement. Guarantee endorsement can be made either by attaching the warrantor into the chain of endorsements or by signing on the reverse side of the bill and outside the chain of endorsements with no other indications. The legal nature of this simple signature that stands outside the chain of endorsements, and whether this signature brings any responsibility to the signee and also whether the signee will have a right to recourse in case of a payment, are highly debated both in Turkish and foreign law doctrines and practices. Most decisions of the Turkish Court of Cassation ignore the legal existence and economic value of the guarantee endorsement. The present study aims to suggest the legal grounds for guarantee endorsement, which has been frequently used in practice in the place of Aval, especially by signing on the reverse side of the bill above the payee’s endorsement. In other words this study aims to ascertain and to determine why these signatures should be deemed valid as guarantee endorsement and therefore bring responsibility without harming the chain of endorsements and eventually why the signee who makes payment should have a right to recourse.