Abstract: Clamp apparatus comprising a base, a rocker arm mounted at a location intermediate first and second portions thereof to the base for pivotal movement in opposition to the base, a first clamp element carried by the first portion, power transfer structure supported movably by the base and having drive and driven ends, a second clamp element carried by the driven end in substantial opposition to the first clamp element, and carried adjacent the second portion, a drive element responsive to application of a first force for exerting a second force to the drive end for pivoting the rocker arm to force the first clamp element against a work piece positioned between the first and second clamp elements, and for moving the power transfer structure to force the second clamp element against the work piece.