Abstract: A device for allowing a worker to lay out parallel lines which are to be spaced apart throughout by a constant distance S, and which lines include parallel but offset sections being joined by intervening angled sections with one of the lines of each offset section being extended to overlap the other by a distance D in order to maintain the lines parallel and spaced throughout by the distance S, the device including a first disc having indicia disposed on one side thereof which correspond to the slope and run of an angled section, and indicia disposed on the other side thereof which corresponds to the overlap distance D with the device further including two other discs, each of which is disposed over one of the surfaces of the first disc and including indicia corresponding to the rise of an angled section, thereby allowing a worker to align the indicia corresponding to the run or slope with that corresponding to the rise of an angled section, the device allowing a worker to obtain directly therefrom the requis