Using Layers as an Organizing Tool

To understand what layers are and why they are so useful, think again about the transparent overlay sheets used in hand drafting. Each overlay is designed to be printed. The bottom sheet might be a basic floor plan. To create an overlay sheet for a structural drawing, the drafter traces over only the lines of the floor plan that the overlay needs and then adds new information pertinent to that sheet. For the next overlay, the drafter performs the same task again. Each sheet, then, contains some information in common as well as data unique to that sheet.

In AutoCAD, using layers allows you to generate all the sheets for a set of overlays from a single file (see Figure 6-1). Nothing needs to be drawn twice or traced. The wall layout is on one layer, and the rooflines are on another. Doors are on a third. You can control the visibility of layers so that you can make all objects residing on a layer temporarily invisible. This feature lets you put all information keyed to a particular floor plan in one DWG file. From that drawing, you can produce a series of derived drawings—such as the foundation plan, the second-floor plan, the reflected ceiling plan, and the roof plan—by making a different combination of layers visible for each drawing or drawing layout (layouts are covered in Chapter 14, “Using Layouts to Set Up a Print”). When you make a print, you decide which layers will be visible. Consequently, in a s....