Abstract: Two extruded aluminum or plastic channel members facing each other and with one confined within the other provide a plumb-rule of basic length and extendable to nearly double that length. The outer channel contains longitudinally spaced spirit level bubbles, a protractor level, and a bulls-eye level bubble all viewable from the exterior through corresponding openings in the back and side walls of the channel, and located free of interference from the inner channel. A counter is incorporated near the upper end of the outer channel and actuated by the extension movement of the inner channel to indicate the extension in increments of distance.