# How to Use a Speed Square | the Basics

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## Introduction: How to Use a Speed Square | the Basics

If you've ever spent much time on a construction site or watching YouTube videos on making things, chances are you've seen a speed square. These triangular devices have been used by makers for decades. Originally invented by Albert J Swanson in 1925, Swanson Speed Squares (affiliate link)have become a household name and it's the square that Dylan grew up learning to woodwork as well. If you are new to woodworking it can be daunting to figure out what tools you may or may not need. There is just a ton of information out there. Which is a good thing, but it's a lot to take in. Hopefully, in this blog, we can show you how to use a speed square to its full potential.

## Step 1: The Differences

Here is the image that pops up when you think of a speed square. This one here is an all-aluminum speed square and what made the household name, Swanson and currently holds the copyrighted name of "speed square".

There are many differences between speed squares, so let's start there. The one on the left is a 20-year-old Swanson, and the one on the right is a newer one that we use daily. They are basically identical but have a few differences like the diamond cut out in the newer one and the scribe lines in the inner triangle. We are going to show you what you can do with these features here, but keep in mind that a lot of squares don't come with said features.

## Step 2: Swanson Speed Square Blue Book

Another thing about the Swanson Speed Square is that they all come with the Swanson Speed Square Blue Book. This book gives you a lot of conversions and shows you everything you need on how to use the speed square. In the back of the book, it gives you all the measurements you need for making rafters, you find the length and width of your building and there ya go. This book goes way more into detail than what we are talking about today, just thought this was super interesting.

## Step 3: 12" Swanson Speed Square

Here is a larger Swanson speed square at 12", and this one is made out of a composite material and is their "speedlite" model. Even though these are super nice and light and easy to use, ours has chipped and is broken in the middle. Just something to keep in mind.

## Step 4: Empire 12" Speed Square

Moving onto another 12" speed square, this one is all aluminum from Empire. This one large scribe marks designed for using the carpenter pencils, doesn't work so good with a regular pencil or pen. Another thing is on the back, it has a nice common rafter conversion chart with runs and degrees. This one isn't really the best for us, we don't build buildings, so the chart or the larger scribe marks aren't a selling point in our case, but it could totally be for you.

## Step 5: Husky Expandable Speed Square

This one is a bit different. This all aluminum speed square from Husky is a bit thicker than most of the squares out there. It's also painted with white lettering which is nice and different, but not to sure about how long the paint will last over time. This one does have nice scribe lines that will work better with a regular pencil or pen. One downside to this one is that it doesn't go the full 7", it goes to a little over 6" which you can barely tell because there isn't a 6 on the square. This can be tricky and will show you why later on. The unique thing about this one though, it extends to turn into the full 12". One thing to keep in mind though is that if you were to drop this on the ground, you might risk bending the extendable part out of square, and then now what's the point. This is super handy though if you are looking into only buying 1, and now you wouldn't have to buy a 7" and a 12".

## Step 6: Most Common Use

The most common use of a speed square is creating a square line. Simply hold the square against the long edge, you can draw a straight, square line. You can hold the square either from the top or bottom, really just personal preference, we both typically hold it from the top.

## Step 7: Making Multiple Lines

Still in this position, you can use that inner opening to make multiple marks using the guide there, and then move the square down the board to make another line. This would be a great layout tool for putting a wall stud in place. If you have a top and bottom plate, you can just transfer those lines and that's the reason for the length of a square. Now those plates are going to be identical.

## Step 8: Using Scribe Marks

You can also use the scribes to make straight lines down the board, just line up the scribe mark to the measures above.

## Step 9: 45° Angles

Let's move beyond 90° angles. Say you want a simple 45° angle. All you have to do it turn the square to where the angled side is lined up with your mark.

## Step 10: Beyond 90° Angles

Now say you want a different angle. Any angle on a 180° plane. On this square is actually says pivot. So place that point (the 90° point on a square) on your mark. Now, pivot the square until your desired angle is lined up with the board. This one is a 15° angle.

## Step 11: Beyond 90° Angles Cont.

What if you need one beyond 90°? This can also be achieve with a speed square! Let's do 105° angle. So, 90 + 15 is 105, make you're 15° mark, but now looking at it from the bottom of the board past 90° to your 15° mark, that's 105°. All in all, subtract 90 from the total angle you want and use that number to make your mark.

## Step 12: Using a Speed Square for Power Tools

Moving away from boards for a second, another really practical use for a speed square is using it for your saw. You should almost alway make sure your saw blade is square. For instance, with a circular saw, making sure there is no power going to the saw, you can push the blade guard back and making sure the blade is square to the bed of the saw. You can do this with any saw as well!

Another thing to think about and check is to make sure the square is actually square. All you have to do is make a 90° line, then flip the square over and make sure that line is lining up right with no gaps. This is just something to look for every now and then.

You can use a speed square as a guide for power tools, mostly done with a circular saw and man is this easy! You can use a square instead of measuring out the perfect line and clamping down a guide rail.

## Step 13: Speed Square for Construction and Roofing

Now let's talk about roof structure and the speed square. This is what a house structure looks like, not to scale, but it gives you the picture. This roof has a 6:12 pitch meaning that every 12" of run, there is 6" of rise. That pitch correlates to the angle of the rafter that hits the ridge. This 6:12 pitch is a 26 1/2° angle. If the pitch was 12:12, the angle would be 45°. Here's how you would line up the speed square to create that angle. The numbers labeled as common are your pitches, so number 1 would be 1:12, 2 is a 2:12.....ours is 6:12, so tilting the speed square until we get to 6, now you have the right angle you can mark and cut. I'm not sure how well I can explain the birdsmouth section in words, so I am going to refer you to the video at the top which this part starts at 17:30.

## Step 14:

That's going to do it for this "How to Use a Speed Square" blog! I hope you got some good information here and you can refer to the video at any point if you get confused. I am such a visual learner that no matter how well you explain something to me, I will not understand until I visually see it in action.

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• ### Puzzles Challenge

Very clear and concise instructional video! I have owned and used Speed-Squares for decades. Recently, I gave one of my (several) 18v DeWalt circular saws to one of my grandsons, who just bought an old house. Also, gave him one of my old S-squares- no manual. Searching thru numerous You-Tube vids, I found this one to be the very BEST! Basic, clear information without "wannabe comic" wanderings. I am a practicing, licensed Architect ... 40 years + in business, with a staff of up to 14 people in earlier years. As the son of an old school master carpenter, I have long been a "tinkerer" in several trades. Couldn't make a living doing them...BUT... knowing how to do, means - don't put up with B...S... about why something can't be done.
This is an EXCELLENT instructional!

I have a few of these. I knew they had other uses other than just 45 and 90 degree angles. I just didn't know how to use them. This will help in future projects. The one thing that I would have liked for you to include would have been an example of the placement of the birdsmouth. In other words measurement from rafter to the point of the first mark for the birdsmouth. (Perhaps that is on another video.) Thank you for doing this! I will check out your YouTube channel.

The placement of the birdsmouth just depends on the width of the building. Thanks for checking us out!

In your article and video, you said a 12:12 pitch is a 45° pitch. That being the case, wouldn't a 6:12 pitch actually be a 22.5° pitch (I/2 of 45°) and not a 26.5° pitch?
Or, am I missing something?

The relationship between angles and the sides of a triangle are not linear, i.e. half the angle is not half the ratio of the sides. In fact, the relationship is based on the tangent function. tan(angle) = rise / run. angle = arctan(rise/run) arctan(6/12) = 26.6°

Many thanks for describing the 'speed square'. I am in the UK, and had never heard of this tool before. Brilliant device. Had woodwork lessons in school in the 1960's and the speed square was never mentioned. Never seen the speed square in any craft, hobby or hardware shops. I am going to buy one through Amazon.

That's crazy! It's commonly referred to as a roofing square or rafter square. But it's just a great tool to have when building anything!

Make sure to get a metal one, the plastic ones are junk, they melt/deform in heat.

Great video.
My understanding is what you call a 2x4 The 4 stands for 3.5" as you mentioned or 1 and 3/4 by 3.5 inches. In metric it is simply 4 cm by 9 cm. It is so easy to add metric measurements and to compute areas and volumes without need to convert. GO METRIC USA. 70% of our industry is already metric :)

OO that's fancy!

This really helped me thank you.