Best Speed Squares and Rafter Squares
The speed square is the cheapest tool in the shop that nobody fully uses. Most people know it marks a square line and a 45 degree angle. The scales printed on the face also lay out rafter cuts, and the fence makes it a cutting guide for a circular saw.
Speed square or combination square
They are different tools and most shops need both.
- Speed square (rafter square). A triangular plate with a fence on one edge. Fast to use, tough, works as a saw guide, and carries printed scales for common rafter and hip or valley cuts. Not adjustable and not a precision measuring tool.
- Combination square. A rule sliding on an adjustable head. This is the tool for setting depth, marking a consistent offset, and checking square properly. Slower to use and more precise.
If you are marking framing, rafters and stair work, the speed square is the one in your back pocket. If you are setting up machinery or laying out joinery, use the combination square.
Size
| Size | Covers | Note |
|---|---|---|
| 7 inch | 2x4 through 2x8, most framing | The standard size, fits a tool belt |
| 12 inch | 2x10, 2x12, wide stock | Bulky but the only size that spans a 2x12 |
| 4 to 5 inch | Trim and small parts | Handy for punch work, limited reach |
A 7 inch square is the right first buy. If you frame with 2x10 or wider regularly, carry a 12 inch as well, because a square that cannot span the board cannot mark across it.
Material
- Aluminum. Light, rustproof, and the most common. Cheaper ones bend if they are dropped on a concrete slab, and a bent square is useless.
- Steel (usually stainless). Heavier and more expensive, holds an edge better as a saw guide, and shrugs off abuse. Worth it if the square lives on a jobsite.
- Plastic or composite. Cheap, light, and it will not mark finished wood. The markings wear fast and the fence flexes, so it is not a precision tool.
Markings: etched beats stamped beats printed
This is the detail that separates a square you still trust in three years from one you have to squint at.
- Laser etched or engraved. Cut into the metal, high contrast, and they do not wear off. The best option and worth paying for.
- Stamped. Pressed into the metal. Long lasting but sometimes hard to read in low light.
- Painted or printed. Wears off within a season of sliding around in a tool bag. Avoid if you can tell the difference when buying.
Features worth having
- Scribe notches. The small slots along the rule let you hold a pencil at a fixed distance and draw a line parallel to an edge. This is the feature people own for years without using, and it is excellent for laying out consistent offsets.
- A level vial. Genuinely useful for checking that a post is plumb, and worth the small extra cost.
- A pivot bracket. Turns the square into a protractor for finding and transferring any angle. Handy for stair work and odd corners.
- Hip, valley and common rafter scales. The reason it is called a rafter square. Read the scale against the fence to get the cut angle for a given pitch without doing trigonometry.
Using it as a saw guide
Hold the fence against the edge of the board and run the shoe of a circular saw against the square's fence to crosscut square. It works because the fence is a true edge and the saw shoe is flat against it. Two cautions: clamp or hold the square firmly, because it will walk, and remember the blade is on the left of the shoe on a sidewinder, so the offcut falls on the side you are not holding.
Frequently asked questions
What is the difference between a speed square and a combination square?
A speed square is a fixed triangle with a fence, used for fast marking and as a saw guide. A combination square has an adjustable head on a rule, used for precision marking, depth setting and checking square. They do different jobs and most shops own both.
How do I use the rafter scales?
Pivot the square so that the pitch you are cutting lines up on the scale, then read the angle it gives you at the edge of the board. Our rafter length and roof pitch calculators give you the numbers if you would rather check the layout arithmetic first.
Is a 7 inch square big enough?
For 2x4, 2x6 and 2x8 work, yes, and it is the size that fits in a tool belt. Once you are marking across 2x10 or 2x12, the 7 inch square cannot span the board and you need the 12 inch.
Do the printed scales wear off?
Painted markings will. Laser etched and engraved markings are cut into the metal and last essentially forever, which is why a slightly more expensive square is often cheaper over its life.
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