How to use a t-square - Straight and accurate drawing of horizontal lines requires a T-square. This tool gets its name from the fact that it is shaped like the letter T. The top, or head, of the T-square is placed along the side of the drawing board. The long strip of the T-square is known as the blade and is 90 degrees to the head of the T-square.
A right-handed drafter works with the head of the T-square against the left side of the drawing board. A left-handed person may place the head of the T-square against the right side of the drawing board. To draw lines, a pencil is guided along the top edge of the blade. The T-square is also used to position paper on a drawing board. The edge of the blade is matched with the horizontal edge of the paper.