When I first started Dunn DIY, I really didn’t know much about working with tools. I had a general sense of what to do, but I was never quite sure if I was using them to their full potential. In Tools 101, I’m sharing everything you need to know about tools, so you can DIY with confidence. Today, we’re talking about the basics of the square and its common uses for DIYers.

When to use

There are several different types of squares—but despite the name, this tool is often shaped like a triangle or an "L". The name "square" is not a reference to the appearance, but to its function: it allows you to find square (90°) angles.

There are lots of different squares from carpenter's squares to T-squares, and they're used by professionals from all different kinds of industries. The squares we work with on Dunn DIY are tools that were mostly designed for construction and roofing, but we're going to focus on their uses for the DIYer. For those of us not building houses, squares are most frequently used for marking a 90° (straight) cut or a 45° (miter) cut on a piece of lumber, but some squares can be used to find any angle. They can also be used for measuring short distances from the ends or sides of a piece of wood (like when marking for screw placement), or for squaring up projects (i.e., making sure your planter bed is a rectangle, not a parallelogram).

There are three different types of square that we’ll be looking at today: Speed Squares, combination squares, and framing squares.


Speed square
  • Fence/lip: The fence runs along the side of the square and allows you to hold the square against the side of a board and determine 90° or 45° from that side.
  • Pivot point/angle: The pivot point is in the 90° angled corner of the triangle. You can find any angle by holding this pivot point against the edge of a board, then pulling the fence side of the square away from the board until the degree marks on the opposite side of the square line up with the edge of the board at the desired degree mark.
  • Ruler/other markings: The ruler along the top of the square will probably be what's used most. Markings such as "seat cuts," "hip/val cuts," "common top cuts" or the like are there for roofers and construction workers, so don't worry about them.
  • Scribe bar: The scribe bar includes notches along a cutout inside of the square. These notches are generally placed 1/4" apart and are positioned a specific distance from the fence (like 3/4"). By positioning a pencil in between these notches and sliding the square up and down along a board, you can draw a straight line a specific distance away from the edge of the board.
Speed square
Combination square
  • Anvil: The anvil is the middle part of the combination square that slides up and down along the ruler. The anvil itself acts as a fence that allows the ruler to find 90° and 45° from the side of the board.
  • Ruler: This is a simple ruler with inch and centimeter markings. In fact, when I need a ruler for a project, I generally just slide out the ruler from this square rather than keeping a second one on hand.
  • Adjustable knob: The adjustable knob allows the ruler to slide up and down inside the fence (or slide out completely). By adjusting the ruler to a specific measurement, you can easily mark the same distance repeatedly, like for lining up screws in a row.
  • Scratch awl/scriber: The awl or scriber is a small metal pin that can be used to scratch a marking onto wood or to make an impression at a specific point to keep a drill bit from wandering.
  • Bubble vial: The bubble vial allows this square to double as a small level. This makes finding square angles while staying level at the same time that much easier.
Framing square
  • Tongue: The tongue is the shorter, narrower length of the "L" shape. 
  • Blade: The blade is the longer, thicker section of the "L" shape.
  • Heel: The heel is the corner between the tongue and the blade.
  • Ruler/other markings: This square, like the speed square, has a lot of extra markings. Aside from rulers that start from both the inside and outside corners of the square, you'll notice various other sets of numbers. Again, these are specific measurements and scales for professional woodworkers and construction workers.

Different types/functions

Speed squares

Speed Squares work as try squares (for finding 90°), miter squares (for finding 45°), and protractors (for finding all the angles in between). “Speed Square” is a brand name, so this type of square is also called a quick square or a rafter square. Speed Squares are designed to measure the pitch of a roof or the angle of stair stringers, which means they’re not entirely accurate; but for our general purposes, they're accurate enough. Speed Squares are useful as a guide for cutting with a circular saw or handsaw when cutting angles outside of the miter box. They can be used for finding any angle, marking a line down the length of a board, or marking specific distances from the side of a board when rip-cutting lumber. 

Functions of a speed square
Combination squares

Combination squares work as try squares, miter squares, and rulers. They are very useful in measuring overhangs. They also lack some level of precision because the adjustable knob has some give to it, and they have fairly short fences. But again, for our purposes this isn't a concern.

functions of a combination square
Framing squares

Framing squares work as try squares and can be used for framing, laying rafters, and working with stairs. They can be used for squaring up larger projects (like a planter bed), and they double as a straightedge, making them ideal for cutting plywood.

functions of a framing square

Our recommendations

If you’re a beginner, a 6” Speed Square is a great place to start. You can easily create straight and miter cuts and quickly find other angles, as well.

If you want to grow your toolkit, a combination square is a great pairing to the 6” Speed Square, especially if you’re looking for a slightly longer tool. I like to use one for making marks for screws because you can adjust the ruler to one setting and quickly make the same mark repeatedly. I also like to pull the ruler out of the square and use it on its own (regular rulers get bent or broken in my tool bag).

If you’re more advanced, a framing square is great to have on hand for larger projects, cutting plywood, and other common homeowner needs.

There’s a right square for every project. Start with the simplest, then invest as you increase your skills and take on larger, more complicated projects.

As you move along in your DIY journey, be sure to check out our other Tools 101 posts: how to use a tape measure, when to use a power drill, what type of drill to buy, and how to use a power drill.