clapper box

This tool-slide holds the clapper box and toolpost, from which the tool can be positioned to cut a straight, flat surface on the top of the workpiece.

Shapers, slotters, and planers often employ a kind of toolholder called a clapper box that swings freely on the return stroke of the ram or bed.

The name shaper relates to the fact that the cutter engages the part on the forward stroke and pulls away from the part on the return stroke, just like the clapper box on a planer shaper.