Speed Square and Framing Square: Two Layout Tools Worth Owning

What is a speed square, and what is a framing square?

A speed square is a small, thick triangle, usually aluminum, about 7 inches on its short sides. One edge has a raised lip, also called a fence, that hooks over the edge of a board. Press the lip against the board and the other edge sits at exactly 90 degrees, ready for a pencil line. The long edge has a degree scale, so the same tool marks 45 degree cuts, roof angles and anything in between.

A framing square is the big brother. It is a flat L made of steel or aluminum, with a long, wide arm called the body and a shorter, narrower arm called the tongue. Both arms carry inch marks, and many framing squares have tables printed on them for roof rafters and stairs. It is too big for a pocket, but it checks large corners and lays out stair steps in a way a small square cannot.

Both tools do one simple job: they tell you what "square" is. Square means two lines meet at exactly 90 degrees. Every wall, cabinet, deck and shelf depends on it. When things are not square, doors stick, shelves rock and gaps show up in the trim.

I'm a licensed architect, and on nearly every job site I visit there is a speed square hanging off someone's toolbelt. It is one of the least expensive tools a carpenter owns and one of the most used.

Why you'll want it

A tape measure tells you how long to cut a board. A square tells you where the cut line goes across the board. Without one, you are guessing, and a cut that is off by a few degrees turns into a visible gap once the piece is installed.

Square cuts every time. With a speed square, you hook the lip on the edge of the board, run a pencil along the other edge, and you have a square line in two seconds. No measuring from both sides, no wandering line.

Angled cuts without a protractor. The degree scale lets you pivot the square from one corner and mark any angle. That covers deck railings, rafters, stair parts and decorative cuts.

A guide for your saw. Hold a speed square tight against the board and run a circular saw along it, and you get a quick, square crosscut without a miter saw. This is the trick that makes a circular saw so useful on a deck or in a yard.

Checking corners. A framing square sits in the corner of a wall frame, a cabinet box or a concrete form and shows right away whether it is square. Its long arms make small errors easy to see.

Stairs and roofs. A framing square, with a pair of small clips called stair gauges, lays out every step on a stair stringer (the sloped board that carries the steps) at the same size. Both squares have scales for roof rafter angles, so you can mark rafter cuts without doing trigonometry.

They last for decades. A good aluminum or steel square has no battery, no motor and almost nothing to break. Many carpenters use the same square for most of their working life.

Where you will use them

• Decks and fences: marking every board end square before cutting.
• Sheds and wall framing: marking stud positions and checking that corners are square before sheathing.
• Stairs: laying out the rise and run of each step on a stringer with a framing square.
• Shelving and storage: marking plywood and boards for clean, square cuts.
• Small repairs: replacing a fence picket, a stair tread or a piece of trim.

Speed square or framing square first?

If you buy one, buy a speed square. It handles most cuts a homeowner makes, fits in a pocket and is one of the least expensive tools in any kit. Add a framing square when you start framing walls, building stairs or checking larger assemblies. On a remodel, I like to see both in the truck.

How to use it

These steps cover the two jobs you will do most: marking a square cut with a speed square, and checking a corner with a framing square.

1. Measure and mark your length. Use a tape measure to find the length you need, and make a small V mark on the board with a sharp pencil. The point of the V is your exact spot.
2. Hook the speed square lip on the board. Press the raised lip firmly against the edge of the board that faces you, with the square lying flat on top.
3. Slide the square to your mark. Move the square along the edge until its straight edge touches the point of your V.
4. Draw the line. Hold the square still with one hand and draw a line along its edge, all the way across the board. This line is square to the edge.
5. Mark the waste side. Draw a small X on the side of the line you will throw away, so you remember to cut on that side and keep the finished piece the right length.
6. Mark an angle when you need one. Put the pivot point (the corner marked "pivot") against the board edge, rotate the square until the degree you need on the long edge lines up with the same board edge, and draw along the square.
7. Check a corner with a framing square. Set the framing square in the inside corner of the frame, body along one side and tongue along the other. If both arms sit tight with no gap, the corner is square.
8. Check big frames by measuring diagonals. For a whole wall or deck frame, measure corner to corner both ways. If the two diagonals match, the frame is square. If not, push the corners of the long diagonal toward each other until they match.
9. Test your square once in a while. Draw a line with the square against a straight edge, flip the square over, and draw again from the same point. If the lines do not match, the square is out and should be replaced.

Tips from the field

• Use a sharp pencil or a marking knife. A thick pencil line can be wider than your error. Sharpen often, or score fine work with a utility knife.
• Mark from the same edge. When marking several boards, always hook the square on the same factory edge so every cut matches.
• Use the 3-4-5 rule for big layouts. Measure 3 feet along one side and 4 feet along the other; if the distance between those two points is exactly 5 feet, the corner is square. Use 6-8-10 for larger areas.
• Keep the lip clean. Dried glue or a dent on the lip throws off every line you draw.
• Hang it, don't toss it. A square dropped on concrete can bend at the corner. Steel framing squares especially should hang on a wall, not ride loose in a truck bed.

Common mistakes

• Letting the lip slip off the edge. If the lip is not tight against the board, the line will be out of square. Press it firmly before you draw.
• Cutting on the wrong side of the line. The saw blade has thickness. Cut on the waste side, or your board ends up short.
• Trusting a damaged square. A bent or chipped square gives a confident wrong answer. Test it and replace it if it fails.
• Reading the wrong scale. Speed squares carry a degree scale and rafter scales side by side. Read the label on the row before you mark.

What to look for when buying

Squares are simple, so the details that matter are few. Here is what I would check.

Size. For a speed square, the 7 inch size is the standard and covers 2x4 and 2x6 lumber. A 12 inch version is handy for wider boards and stair work. Framing squares come in a common large size that suits wall and stair layout; smaller versions exist for cabinet work.

Material. Aluminum is light and does not rust. Steel framing squares are stiff and wear well but need care to avoid rust. Skip thin plastic squares for carpentry; they flex, and any chip on the edge ruins their accuracy.

A solid lip. On a speed square, the lip should be thick, straight and long enough to hook a board firmly. This is what makes the tool fast.

Markings that last. Look for stamped, engraved or deeply printed markings with good contrast. Painted-on marks can wear away in a season.

Accuracy. A square is only useful if it is truly square. Do the flip test at home and return any square that fails.

Extras. Rafter scales, stair tables and reference books are useful once you frame a roof or build stairs. They are a bonus, not a reason to pay more on day one.

Tier. Both tools are inexpensive. Even the well-known brands sit in the budget tier, so there is little reason to gamble on an unknown brand to save a small amount.

The table below sums up the key specs to compare.

Key specs to look for

Where to get it

For this guide I'm featuring the Swanson S0101 Speed Square. According to the product listing, it is a 7 inch aluminum layout square made in the USA, machined to a true 45 and 90 degree corner, and it ships with Swanson's small blue reference book for roof and stair layout. Swanson is the company that introduced the speed square, and its markings are the pattern most other squares follow. It sits in the budget tier.

Click through to check today's price and read the current reviews on Amazon. When you are ready for a framing square, look for a steel or aluminum one in the standard large size with clear, engraved inch marks on both faces, and add a pair of stair gauges if you plan to build steps.

A square works best alongside a good tape measure or a laser distance meter for long runs. For a full starter set, see the new homeowner toolkit.