Abstract: A base defining an upwardly facing sheet supporting surface and an elongated support member is mounted on the base and projects upwardly from the sheet support surface. The support member includes spacer structure spacing portions of the support member from the base to define an open slot between the base and the spaced portions of the support member. A pair of aligned support blocks are supported from the support member above the opposite end portions of the slot and an elongated head extends between and is removably journaled from the support blocks. The portions of the support member spaced above the base define upstanding sleeve bores therein normal and opening into the slot and bearing sleeves are mounted in the sleeve bores and have elongated punch members reciprocately disposed therein. The base defines die bores below the slot and opening into the latter aligned with the sleeve bores. Die sleeves are disposed in the die bores.