Blueprint reading; a practical manual of instruction in blueprint reading through the analysis of typical plates with reference to mechanical drawing conventions and methods, the laws of projection, etc (1919)
Fairfield, Howard Parker, 1858-, Kenison, Ervin, Waite, Edward B. (Edward Broughton), 1873-, American Technical Society · Chicago, American technical society · leaf 302
and this is usually abbreviatedto GL. The projections may be placed at any convenient distanceabove or below the GL, unless these distances are given in any prob-lem. In beginning all ordinary projection work, it is customaryto show the GL as a horizontal line between the front elevation andplan…
Mechanical drawing · Blueprinting
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