re: Hand Tools - Some New Some Old

Close enough Madts ….. I guess…
It is for taking the angle, every couple of feet, between the edge of the last fastened plank and the face of the rib above or below it where the next plank will go. It is designed to be used one handed in the left hand to leave your right hand free to record the angles on a spiling board. The angles are then transferred to the cut line on the new plank and the edge is cut on the bandsaw with an ever-changing bevel. Pretty simple really……. :-)