The Carpenter's square is also known as a steel square and it is used for measurements, especially right angles. The square consists of a long arm and and a shorter one that are perpendicular to each other at exactly 90°.
The long arm is referred as the blade of the square and the shorter arm is referred to as the tongue when the carpenter's square is being used in timber frame joinery.
The Carpenter's square is used for:
- The laying out of rafters according to a rafter table.
- The laying out of treads and risers on a stringer when staircases are being framed.
- Measuring and marking out mortise and tenons in timber frame joinery.