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AutoCAD® 2012 FOR DUMMIES® by David Byrnes

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Rocking with Blocks

First, a little more block theory, and then you can rock right into those blocks. To use a block in a drawing, you need two things: a block definition and one or more block insertions. AutoCAD doesn't always make the distinction between these two things very clear, but you need to understand the difference to avoid terminal confusion about blocks. (Maybe this syndrome should be called blockheadedness?)

A block definition lives in an invisible area of your drawing file called the block table. (It's one of those sets of named symbols that I describe in Chapter 6.) The block table is like a book of graphical recipes for making different kinds of blocks. Each block definition is like a recipe for making one kind of block. When you insert a block, as described in the section “Inserting blocks,” later in this chapter, AutoCAD creates a special object called a block reference. The block reference points to the recipe and tells AutoCAD, “Hey, draw me according to the instructions in this recipe!”

Although a block may look like a collection of objects stored together and given a name, it's really a graphical recipe (the block definition) plus one or more pointers to that recipe (one or more block references). Each time you insert a particular block, you create another pointer to the same recipe.

The advantages of blocks include

  • Grouping objects together when they belong together logically: You can draw a screw using lines and arcs and then make a block definition out ...

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