PURPOSE: To surely prevent blades from dropping by bonding the lower surfaces of rubber blocks to an upper steel plate and the side faces of the blocks to the side faces of a blade or a ruling blade, in a trimming die for use in a plate punch.

CONSTITUTION: In a trimming die for punching a case of a VCR cassette and the like made of a plastic sheet, steel plates 14, 15 are bonded to the upper and lower surfaces of plywood 1, and are fixed integral with each other using screws 17.... The plywood 1 and the upper and lower steel plates 14, 15 are cut at the required parts by laser beams so that a blade 11 and a ruling blade 12 can be placed lengthwise and crosswise, and the blade 11 and the ruling blade 12 are fitted into a variety of oblong holes formed. In order to prevent the blade 11 and the ruling blade 12 from dropping, rubber blocks 16, 16 are bonded to the side walls of the blade 11 and the ruling blade 12 and to the upper surface of the steel plate 14 with a rubber type adhesive.