A converting machine adapted to perform at least one step in the production of cases from rectangular blanks of corrugated board or similar sheet material, and of the kind which has a number of parts which can be adjusted laterally (that is in a direction transverse to the direction in which work passes through the machines) for the purpose of making cases of different size from blanks of different size, characterised by the provision of a laterally movable device which can be located at a position to be assumed by an adjustable part, a motor for moving said part laterally to the left or right, there being first switch means and first switch actuating means, one being movable with said part and the other being movable with said device, whereby as the part is moved into register with said device said first switch means is actuated to stop said motor, and second switch means and second switch actuating means, one being movable with said part and the other being movable with said device whereby said second switch means is actuated by movement of said device out of register with said part to signal to said motor in which direction the part should be moved when next adjusted in order to come into register once again with said device.