The invention relates to clamping apparatus for a workpiece. The apparatus includes first and second jaws, one of which is movable by operator operation of a lever assembly and locking means are provided to selectively lock the movable jaw in position. The locking means can be actuated by the operator's foot thereby leaving the operator's hands free to perform work on the workpiece. An engagement system is also provided in order to allow additional accessory components to be selectively fitted to the apparatus for use in particular work operations.