Abstract: The invention concerns a device for carrying out an operation, according to a given pitch, on a uniformeously and continuously moving web.The device comprises a first block provided with a tool, which describes in a reciprocating motion a small arc of circle around a stationary horizontal axis parallel to the axis of the movement of the web, to make periodically cooperate said tool with a member complementary to said tool, provided on a second block, said first block being connected to said second block at the level of said stationary axis, both blocks such connected and hung to a stationary frame, being driven parallel to the movement axis of said web in a reciprocating motion, the period of which is identical to the period of the motion around said stationary axis.Application to the perforation, the cutting, the embossing, the notching, the stitching of webs.