Collateral promise

if I go to a shop with a joiner, and say to the master, 'I will see you paid for the articles with which you trust this man;' here, though I am liable upon proof of this undertaking, yet it is not in the character of the original debtor, for the joiner who received the goods is the original debtor; bit it is on account of what the law terms my collateral promise; which cannot be proved by the testimony of the party interested, but, may by a note in writing, or by some indifferent witness to the transaction.

A promise is collateral if another is the primary or principal debtor, and the relations of debtor and creditor remain unchanged both as to the right and the remedy, and no trust is created by the transaction. 17 111. 507; 82 111. App. 308.