Abstract: A slide-fastener assembly comprising a pair of longitudinally extending and parallel tapes having adjacent edges carrying respective coupling coils that form coupling heads and that are interleaved with one another is gapped by advancing the assembly in steps through a punching location, engaging the coils upstream and downstream of the location by respective upstream and downstream grippers and holding the assembly stationary in the station between steps, and punching the heads off the coils between the grippers while the assembly is held stationary in the station. The grippers are displaced apart to longitudinally tension the coils after engaging the grippers with the coils and before punching the heads off the coils. Thus the upstream gripper is displaced upstream and the downstream gripper downstream, slightly stretching and tensioning the tape assembly.