§ 15-104. Discharge of one obligor, with reservations. Subject to the
provisions of section 15-103, the obligee's release or discharge of one
or more of several obligors, or of one or more of joint, or of joint and
several obligors shall not discharge co-obligors, against whom the
obligee in writing and as part of the same transaction as the release or
discharge, expressly reserves his rights; and in the absence of such a
reservation of rights shall discharge co-obligors only to the extent
provided in section 15-105.