t-square

noun

1. a T-shaped ruler, used primarily in mechanical drawing, having a short crosspiece that slides along the edge of the drawing board as a guide to the perpendicular longer section in making parallel lines, right angles, etc., and as a support for triangles.

noun

1. a T-shaped ruler used in mechanical drawing, consisting of a short crosspiece, which slides along the edge of the drawing board, and a long horizontal piece: used for drawing horizontal lines and to support set squares when drawing vertical and inclined lines