You just use the "edge" of the light to cut. If you drag a baseball bat through sand, the edge of the cut "channel" is much sharper and narrower than the baseb

You just use the "edge" of the light to cut. If you drag a baseball bat through sand, the edge of the cut "channel" is much sharper and narrower than the baseball bat. Now offset the baseball bat a bit and draw another line which is partially overlapped over the first one. You will get the intersection of the two baseball bat wide channels, but it will be much narrower.