Abstract: A fastening apparatus such as a stitcher or stapler for fastening a quantity of individual sheets together to form a pack is disclosed. The apparatus as aforesaid includes a tray for receiving sheets to be fastened, there being jogging means to co-align the sheet edges preparatory to fastening, and at least two stitching or stapling heads for driving staples through the assembled sheets. A transport ejects the finished pack into an output bin. Apparatus for selectively uncoupling one of the stitching heads from the head driving mechanism to thereby disable the head without removing or disassembling the head is provided.