Abstract: A bracket between the head of a tripod and a primary surveying instrument has a bottom ring provided with a disc, a collar rotatable on the disc and a top collar-retaining ring releasably attached to the bottom ring. A plate, integral with and extending laterally of the collar has a lip which supports an inclined, removable shelf which is, in turn adaptable for having a secondary instrument detachably mounted thereon. A fastener is interposed between a boss on the primary instrument and a stud rigid to the tripod head within a cavity of the latter that receives a flange on the bottom ring.