The Framing Square & Angles

The framing square — and its handy cousin the speed square — is a layout powerhouse.

What they do

• Mark square (90°) lines and 45° angles fast.
• A speed square has degree markings to lay out any angle and works as a saw guide.
• The framing square has scales for laying out rafters and stairs.

Common angles

• 90° for square corners, 45° for miters.
• Roof and stair angles come from the rise and run.

Going Deeper (Intermediate)

The framing square (body + tongue) lays out rafters, stairs, and angles, with rafter and stair tables stamped right on it. Add stair gauges (hex nuts) to repeat an angle, and a speed square for fast cut marks.

Advanced / Pro-Level

Layout that depends on the square:

• Rafters: "step off" the rise/run per foot, mark plumb, seat (birdsmouth), and tail cuts; the rafter table gives length per foot of run; hip/valley and jack rafters use their own scales.
• Stairs: total rise ÷ ideal riser (~7″) → number of risers → exact riser height; then run. Code caps riser ~7¾″ max, tread ~10″ min (the "7-11" comfort rule).
• The speed square has degree, common, and hip/valley scales; behind it all is simple trig (tan = rise/run).

Practice Challenge

A staircase must climb a total rise of 108″. Using a ~7″ ideal riser, how many risers and what riser height? (Answer: 108 ÷ 7 ≈ 15.4, so use 15 risers; 108 ÷ 15 = 7.2″ per riser (within the ~7¾″ max). Then size treads (~10–11″) — stair math always starts from total rise ÷ target riser, rounded to whole risers.)

In Practice

Cutting a 45° miter for trim? Set your speed square to 45, run the saw along it, and the cut is dead-on — far faster and more accurate than eyeballing the angle.

Common Mistakes to Avoid

• Eyeballing angles instead of using the square
• Reading the wrong scale on a framing square
• Not using the square as a saw guide

Takeaway: Use a speed square for fast 90° and 45° marks and as a saw guide; the framing square lays out rafters and stairs.

Educational overview — confirm structural and layout specifics with the project plans and engineer.