Wallis, Rolland S. [from old catalog], Iowa state college of agriculture and mechanic arts, Ames. Dept. of engineering extension. [from old catalog] · Ames, Iowa, Engineering extension department, Iowa state college · leaf 13
Sw/n … Fig. 11.—Erasing shields. different sizes and shapes. In use it is so placed on the drawing as toconfine the erasure to the part to be erased. Ruling Pen.—Ink lines of uniform thickness are obtained by theuse of a ruling pen moved in contact with the edge of a straight-edge,
Mechanical drawing
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