Pencils are the basic tool for mechanical drawing. Pencilling is the first basic skill in mechanical drawing.
Anthony, Gardner C. Elements of Mechanical Drawing (Boston, MA: D. C. Heath & Co., 1904)
732×2400, 223.5 KiB
312×1024, 37.4 KiB
195×640, 20.1 KiB
97×320, 7.9 KiB