Here's a quick post in praise of 1-2-3 blocks. They come in pairs, they're quite affordable, and I think you should at least know about them. Most woodworkers haven't heard of them, most woodworkers don't have them. They come from the machine shop, but why should those guys have all the cool precision stuff to themselves? Other items that woodworkers have lifted from the machine shop include the combination square, the engineer's square, the dial indicator (for setting up table saws and planers), the dial caliper (for measuring thickness) and the precision straightedge (used both to check machine tables and the straightness of wood workpieces). This is another machine shop item we should be thinking about borrowing.