T-square.
A draftsman's ruler.
The blade is set at right angles to the helve, and the latter slips along the edge of the drawing-board, which forms a guide.
The helve is made of two parallel pieces, in one of which the blade is mortised.
The other portion of the helve is adjustable on the setscrew to any angle, so as to rule parallel oblique lines, or to form an oblique base for the triangles, which are the usual rulers in plotting and projecting.
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T-square. |
Fig 6716 has a shifting member on one side of its tongue, so as to give the latter any angle with the base line of the drawing.
The tangent-screw and protractor admit accurate angular adjustment.
