Abstract: A positioning device for use with a table saw including a worktable with a transverse beam transversal to the saw, along which a workpiece stop member may slide. The device has an elongated support fixed to the transverse beam of the worktable. A plurality of block members are slidably mounted along the support and are lockable anywhere on this support. An alignment arm is connected to the stop member so as to be movable therewith. This arm has at least one protuberance that is engageable with any preselected block member to lock the stop member in a given position away from the saw. The device allows for easy and infinitely precise positioning of the alignment arm and stop member plate for a workpiece placed on the worktable. It further allows for a rapid "programming" of the positioning of a plurality of workpieces to be sawed.