It’s possible to draw a fairly straight line with a pencil, but if you want to be accurate, you must use a ruler or straightedge to guide the pencil as you draw. Similarly, if you want to saw a piece of wood (or plastic, or PVC pipe) so that the cut is as straight as possible, you need a tool to help you guide the saw. A ruler won’t help (don’t try, you’ll just ruin the ruler). Instead, an inexpensive tool called a miter box (sometimes spelled mitre) will do the trick. In this article, I’ll explain what a miter box is, and how to use it.
Technique originally posted on CRAFT.