The relation of suretyship arises where besides an obligee, as, for instance a creditor, and the principal obligor, as a debtor, there is another person who becomes answerable for the debt or default of the principal obligor, and who is called a surety.

The contract of a surety is so peculiar as to form the subject of a separate branch of law. It will be remembered that this contract is one of those which, under the Statute of Frauds, must be in writing, in order to be enforceable. The principle of the law of Suretyship chiefly to be noticed is that if the creditor acts in such a manner as might affect the position of the surety and increase his liability, the surety is discharged. Therefore, if in a contract between A and B, C becomes surety for performance of B's part, A must proceed with great caution in all matters affecting his relations with B. In some states if the surety requests the creditor to bring suit against the debtor, and the creditor re-fuses to do so, the surety will be discharged. Written requests to sue are provided for by law in some states. Lack of diligence in prosecuting a suit may forfeit the creditor's right against the surety. The release of one surety discharges co-sureties from so much of the original debt as the person discharged could have been compelled to pay. So if the property of the debtor is held for security, and is surrendered, the creditor loses his claim against the surety to the extent of the value of the property. The point chiefly to be regarded as most likely to affect building contracts is that any material alteration in the contract between the creditor and the principal which would extend the liability of the surety beyond the terms of his original agreement, and to which the surety does not assent, discharges the surety.