AutoCAD 2015 and AutoCAD LT 2015: No Experience Required: Autodesk Official Press

Chapter 6 Using Layers to Organize Your Drawing

Before the age of computers, drafters used sets of transparent overlays on their drafting tables to compose document sets of multiple disciplines. Each design discipline, such as architecture, electrical, plumbing, and HVAC, were drawn on an individual overlay. Each overlay had small holes punched near the corners so the drafter could position the overlay onto buttons, called registration points, that were taped to the drawing board. Because all overlays had holes punched at the same locations with respect to the drawing, information on the set of overlays was kept in alignment. Thanks to this tight integration, plan sheets were more easily produced because it was not necessary to redraw individual ...