This was such an ingenious product I had to order one. The Hang-O-Matic is a combination tape measure, level, and markers that make mounting things with two hangers a snap. You first measure the distance between the midpoints of the hangers and slide the marker on the right to the proper spot on the tape measure. Place the Hang-O-Matic on the wall, adjust it until it's level, then push the markers into the wall to make a slight indentation, which becomes the exact spots to nail in the hooks. There's a 90-second video at the link below that will show you better than I can explain.