The ingeniously simple speed square is the most practical and useful hand tool for any carpenter or do-it-yourselfer.

Also called a rafter square, this multi-purpose triangular carpenters’ tool packs so many features into such a small tool that at first glance it might be confusing how to use it.

So, we’ve broken down its five uses for you:

1. Make accurate cuts. Because of its triangular shape, a speed square is great for making square crosscuts or 45-degree lines. Simply line up the edge to a board to cut the right angle every time.

2. Mark angles. A speed square has a pivot point, so you hold it against the edge of the board and rotate it to mark any angle. For example, let’s say we want to mark a 30-degree angle. Simply hold the edge of the speed square against the edge of a board, then pivot it to line up with the 30-degree mark on the speed square.

3. Use it as a scribing tool. Let’s say you want to make a parallel line one inch from the edge of a board. A speed square has quarter-inch notches on its inside, so you can put your pencil in the one-inch notch and slide it along the board. Then, you’ll have an even line one inch from the edge.

4. Mark the width of 2-by-4.A speed square has a diamond cutout exactly three and a half inches to the edge of the square, which is exactly the width of a 2-by-4. So if you put your pencil in there and slide it along that line, this will is exactly the width of a two-by-four.

5. Use it as a saw guide. Probably the most useful and obviously practical application of a speed square is as a saw guide. Just take the square, hold it against the board’s edge and guide the saw right against the square. You’ll get a straight cut every time!