T-square

A T-square or straightedge (also T-rail - because of the similarity with the letter "T ") is a character device that is used in combination with drawing board and drawing instruments. The tear bar assists you to draw horizontal and parallel lines. It serves as a basis for drawing triangles and templates that are applied to it to draw parallels and non-horizontal straight line and to position images with templates. A head portion at the edge of the tear, the tear board rail is moved vertically up and down.

Typical materials are wood and plastics, and metal (which allows cutting of the rail). The length is typically 50-70 cm, but may be considerably more. Special tear rails are provided with an adjustable head which allows the fixed setting of angles.

In the field of pure drawing and fabrication of templates for offset printing, the tear bar was popular as a drafting machine, despite its simplicity, as it allows for greater accuracy when creating a drawing.

The image Caspar David Friedrich in his studio of Georg Friedrich Kersting with T-square in the background ( Mannheim version of 1819).

Straightedge plastic with division (part of) Title