Abstract: Apparatus for releasably adjusting a position of a first portion of a device relative to a second portion of the device. The first portion includes a first surface, and the second portion includes a second surface. A workpiece support surface is defined by the first and second surfaces, and the first surface is rotatable relative to the second surface. A locking mechanism is provided to selectively restrain rotation of the first surface relative to the second surface. An indexing mechanism optionally is provided including a detent mechanism which selectively restrains rotation of the first surface relative to the second surface in one of a plurality of predetermined positions.