Hung pictures look best if they are grouped, and if you line them up along their edges: top, bottom, or sides.  Because most pictures are framed differently, this is not as easy as it looks, and the Hang & Level will take the guesswork out of getting it right, as well as the annoyance of poking more and more holes into your walls, or telling your spouse, ‘no, move it a little more to the left.  No, that’s too far.’  You get the idea.

Get one.