To remarkably simplify the structure of a device to suit a lateral perforation position to a lateral pleat line position during the operation of a folding machine capable of being operated in various types of folding modes.

Boring tools 36, 1, 37, 1, 38, and 1 and boring seat bars 36, 2, 37, 2, 38, and 2 are installed on a single or a plurality of boring bridges 27 disposed coaxially with boring shells 3 and 4. In addition one boring shell 4 is adjustable relative to the other boring shell 3.