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6 things you (probably) didn’t know a speed square can do

You can't go wrong with these right angles

Speed square is a useful tool when working with wood Credit: Getty Images / AMLBox

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Speed squares are one of the more common tools in any homeowner's toolbox. Even if you don’t have one, you know what it looks like—the triangular marking tool with a flat lip on one edge.

Because of its versatility and relative ease of use, a good speed square can be one of the most useful marking tools in your collection.

Speed squares are used the world over to draw straight lines at a right angle to the edge of a board, usually before cutting off the end of said board with a circular saw. Whenever I cut dimensional lumber down to length, a speed square is one of the first tools I grab.

Most people also know that you can use a speed square to draw a 45-degree line by drawing along the long edge of the triangle rather than the short. But drawing 90 and 45-degree lines isn’t all speed squares bring to your tool arsenal.

Here are six other tasks you can use a speed square for, which makes it much more versatile than a set square, which is a basic marking triangle, or a T-square, which is a straight-edge for drawing 90-degree lines.

1. Use it as a guide for your saw

One of my favorite uses for a speed square is as a straight-edge guide when cutting. After you’ve drawn your cut line, position your saw for the cut and bring the speed square right up to the edge of the saw plate.

You can clamp the speed square in place, then just run the saw along the edge of the square. You’ll get a perfectly straight cut, every time.

In my experience, this technique works best with a circular saw and a jigsaw, but I’ve also done it with hand saws and a sawzall.

2. Draw angled lines with the protractor marks

Not only can you create 90-and 45-degree lines with a speed square; you can measure other angles as well.
Credit: Getty Images / Piotr Wytrazek

Not only can you create 90-and 45-degree lines with a speed square, you can measure other angles as well.

Speed squares aren’t just able to draw 90- and 45-degree lines. They can do all of the other angles as well. To draw a different angle, there are two sets of marks that you need to look for.

On the long side of the triangle are numbered degree markers that are all relative to the normal 90-degree line that you would draw with the square. The other important mark is at the point of the triangle across from the long side. It’s a small divot labelled “pivot.”

Position the lip of the speed square along the edge of your board with the “pivot” corner where you want your line to start. Holding the pivot corner firmly in place, rotate the speed square so that the degree marker you need is lined up on the same edge as the pivot point.

For example, if you’re trying to make a 35-degree angle, then make sure the 35 dash is on the edge of the board. Then draw your line.

3. Draw long rip lines down your board

Rip lines run down the length of the board, allowing you to cut longer strips. A speed square makes marking these long lines a breeze.

Look for the small triangle cutout of the square. On the inside of that triangle are small dashes with cutouts for your pencil tip. There is also a pencil cutout at the 3.5-inch mark on the square, in the shape of a diamond, which is used to draw a line that’s the exact width of a 2x4.

To draw a line parallel to an edge, set the lip of the speed square flat against that edge. Place your pencil in the appropriate cutout for your desired width, and drag the entire square down the length of the board, keeping the lip pressed tight to the edge.

Voila! A perfectly straight rip line.

Rip lines aren’t just for cutting. They can also serve as guidelines to align pieces of wood before fastening.

4. Check almost anything to make sure it is square

Speed squares are a quick and easy way to check if what you're working on is square.
Credit: Getty Images / AMLBox

Speed squares are a quick and easy way to check if what you’re working on is square.

Speed squares are a quick and easy way to check if what you’re working on is square. Press the lip against one side of a right angle, either inside or outside, and check if there is any space along the opposite side. If there is space along the top or bottom of the speed square, then your project doesn’t have a 90-degree angle.

While this technique is commonly used to check corners of boxes or the alignments of studs, it can also be used to make sure that your saw blades are square to the tabletop, plate, or fence.

5. Draw easy circles

Believe it or not, speed squares aren’t just about straight lines and sharp angles. They can help you draw circles as well.

The first step is to drive a nail or screw partway into the board in the exact center of where you want your circle.

From there, put the small pivot divot against the nail, holding it firm. Find the scribe mark that matches the radius (not diameter) of the circle you want to draw and insert your pencil.

Finally, spin the square around the nail, keeping firm contact. 360 degrees later, you’ll have a perfect circle with your exact radius.

6. Measure angles for rafters

Photo of angular wooden rafters supporting a painted white ceiling.
Credit: Getty Images / nikkimeel

Speed squares are designed to specifically measure the angles required to cut rafters for roofs of all different pitches—although the average homeowner will never need to do this task.

Most homeowners won’t ever need to do this, and it’s a bit hard to explain unless you’re familiar with roofing. But speed squares are designed to specifically measure the angles required to cut rafters for roofs of all different pitches. The long channel along the hypotenuse of the triangle has markings that correspond to all of the different roof pitches.

If this is something you need or want to learn to do, there are many videos online showing exactly how it works.

Believe it or not, your speed square may not actually be square

I found out that my cheap box store speed square wasn’t square when trying to align my table saw blade. The cuts just weren’t coming out right, and, turns out, the square I was using to measure was off by about half a degree.

Half a degree doesn’t matter for a lot of projects, but when you’re getting into precision work, it makes a big difference.

Here is a simple trick to find out if your speed square is actually square:

First, grab a board with a perfectly straight edge. This can be a piece of plywood with a factory edge or a board that you’ve jointed yourself.

Use the speed square to draw a 90-degree line from the edge, six inches long. Flip the speed square over and draw a second line about a quarter of an inch away, creating parallel lines.

Measure the distance between those lines at several points. If the distances are the same, then congratulations. Your square is square.

If there’s any variability, however, then your square isn’t, and it may be time for an upgrade.

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