I
In measurement, a device consisting of two straightedges set at a right angle.
It is used by carpenters and machinists to check the correctness of right angles, as a guide when drawing lines on materials before cutting, or for locating holes. In mechanical drawing or drafting, a T-shaped instrument known as a T square is used to establish a horizontal reference on the drafting board.
II
[c mediumvioletred] (as used in expressions)
{{link=Red Square">Red Square
square dance
Square Deal
Tiananmen Square
least squares method