Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 39
Use of Tkiangle and Square. Right-angled triangles constructed of wood, hard rubber, celluloid, or metalare very useful in connection with a straight-edge, or ruler, in drawing linesparallel or perpendicular to other lines. To draw lines parallel to each other, place any edge of the triangle in… … Fig. 76 thumb and little finger of the left hand, and the triangle with the other threefingers; with a pencil or pen in the right hand, draw a line along one of thefree edges of the triangle; withdraw the pressure of the three fingers upon thetriangle, and slide it along the edge of the ruler,…
Mechanical drawing
Internet Archive · Library of Congress · Public Domain Mark 1.0. Free to use for anything.
