ABSTRACT
The aim of the workshop engineer should be to give careful thought to each job and try to fulfil the obligations which have been left unwritten on the drawing, but which are as important as the most accurate size relationship. The methods which are most convenient for verifying flatness are either to test the surface against another surface which is known to be flat or testing with a straightedge. A surface plate has a surface of proved flatness, and when testing, the top of the plate should first be rubbed with a thin smear of a paste made up of red lead and oil. The protractor head of the combination square has its own scale of degrees marked on it, and will be found capable of dealing with most of the angular testing encountered. Depending upon the character of the work, it will be necessary to employ a variety of methods for testing the parallelism of two surfaces.
