1,187,173. Severing board on a wound-hoard machine. M. KROFTA. 5 June, 1968 [7 June, 1967], No. 26770/68. Heading D2A. A device for severing and separating board mat from the forming roll by jets of a pressure medium released from several nozzles attached at intervals along a pressure pipe, the pipe being located outside of, and adjacent to the forming roll, parallel to the roll's axis, movable lengthwise, and rotatable about its own long axis. The pipe may be supported at both ends by swivel bearings, and on at least one end carries a lever extendable into the reach of the forming roll circumference to contact and be carried along by a peg located on the forming roll, rotating the pressure pipe about its long axis and, during that movement, the pressure pipe carrying the nozzles is pushed lengthwise by a device, e.g. a lever or pressure piston, and at the end of such movement is returned by a secondary force, e.g. a spring. A guard may be placed around the pressure pipe, in the form of a pipe with a slot, which slot is adjustable in width, and located in front of the nozzles, one of the two adjustable guard plates preferably being movable to close the slot after cut-off. Air-jets may be incorporated into the roll to assist in the removal of the board. An electrical control system is described, the cycle being initiated by an electrical sensor sensing the thickness of the board.