AutoCAD® 2009 & AutoCAD LT® 2009 Bible

Chapter 18. Working with Blocks and Attributes

As you draw, you'll find that you often need to place the same group of objects several times in a drawing. An architect needs to place windows and doors many times in a plan layout of a house. An electrical engineer places electrical symbols in a drawing again and again. A mechanical model may include nuts, bolts, and surface finish symbols many times in a drawing. Blocks are groups of objects that you save and name so that you can insert them in your drawing whenever you need them. A block is one object, regardless of the number of individual objects that were used to create it. Because it's one object, you can easily move, copy, scale, or rotate it. However, if necessary, you can explode a block to obtain the original individual objects.

A great advantage of blocks is that by changing the block definition, you can update all the instances of that block in that drawing. Another advantage of blocks is that they reduce the size of the drawing file. A drawing stores the definition of a block only once, along with a simple reference to the block each time it's inserted, instead of storing each individual object in each block in the drawing database.

As soon as you have a block in a drawing, you can work with it as with any other object. You can snap to object snaps of the individual objects within blocks, as well as trim and extend to objects within blocks, even though you can't edit the individual objects. For example, you can draw a line ...