La palabra del día: Aval

Masculine noun. In Business and Legal Spanish aval is the person or thing that guarantees the payment of a credit, serves as a guarantee of the fulfillment of a certain thing or is responsible for the conduct of another person, normally by means of his signature. E.g.: De hecho, se ofreció al banco una garantía en forma de aval sobre el suelo y todos los activos fijos, así como siete letras de cambio: In fact a collateral in the form of a pledge on land and on all fixed assets was given to the bank, as well as seven bills of exchange.
On a more general note aval can be translated as endorsement.
The verb is avalar. dc