AutoCAD 2005 for Dummies

more easily select them for copying, moving, and so on, use the AutoCAD group feature. Type Group and press Enter to open the Group Manager dialog box. Then select some objects, click the Create Group button, and type a name for the group. When you’re editing drawings containing groups, press Ctrl+H to toggle “group-ness” on or off. If you’ve toggled “group-ness” on, picking any object in a group selects all objects in the group. If you’ve toggled it off, picking an object selects only that object, even if it happens to be a member of a group.

Creating block definitions

To create a block definition from objects in the current drawing, use the Block Definition dialog box. (The other way to create a block definition is by inserting another drawing file into your current drawing as a block, which I explain in the next section.) The following steps show you how to create a block definition using the Block Definition dialog box: 

1. Click the Make Block button on the Draw toolbar.

The Block Definition dialog box appears (see Figure 13-1).

Figure 13-1: The Block Definition dialog box.

  Layers matter when you create the objects that makes up a block. Block geometry created on most layers retains the characteristics, such as color and linetype, of those layers. But if you create a block using geometry on Layer 0, that geometry has no characteristics, such as color and linetype of its own; chameleon-like, it takes on the features of the layer into which it’s inserted.

2. Type the block definition’s name in the Name text entry box.

If you type the name of an existing block definition, AutoCAD replaces that block definition with the new group of objects you select. This process is called block redefinition.

  To see a list of the names of all the current blocks in your drawing, pull down the Name list.

3. Specify the base point, also known as the insertion point, of the block, using either of the following methods:

 • Enter the coordinates of the insertion point in the X, Y, and Z text boxes.

 • Click the Pick Point button and then select a point on the screen. (In this case, use an object snap or other precision technique, as described in Chapter 4, to grab a specific point on one of the block’s objects.)

The base point is the point on the block by which you insert it later, as I describe in the next section.

  Use an obvious and consistent point on the group of objects for the base point, such as the lower-left corner, so that you know what to expect when you insert the block.

4. Click the Select Objects button and then select the objects that you want as part of the block.

AutoCAD uses the selected objects to create a block definition. Figure 13-2 shows the base point and group of selected objects during the process of creating a new block definition.

Figure 13-2: Building a block.

5. Click a radio button to tell AutoCAD what to do with the objects used to define the block: Retain them in place, Convert them into a block instance, or Delete them.

The default choice, Convert To Block, is usually the best. See Step 9 for a description of what happens with each choice.

6. Choose Create Icon From Block Geometry in the Preview Icon area.

Go ahead and create the icon; it will help you and others find the right block to use later. 

7. Specify the Insert units to which the block will be scaled in the Drag-and-Drop Units drop-down menu.

When you or someone else drags the block from one drawing into another via the DesignCenter palette (see Chapter 4) or Tool Palette (described later in this chapter), the units you specify here and the units of the drawing you’re dragging into will control the default insertion scale factor.

8. Enter the block Description.

Now is the time to think like a database manager and enter a useful description that will identify the block to yourself and others.

9. Click OK to complete the block definition process.

If you typed the name of an existing block definition in Step 2, AutoCAD warns you that you’ll redefine that block definition. Click Yes to redefine, which will update all instances of the block in the current drawing to match the changed block definition.

AutoCAD stores the block definition in the current drawing’s block table. If you chose the Convert To Block radio button (the default) in Step 5, AutoCAD also creates a block insert pointing to the new block definition — the objects look the same on-screen, but now they’re an instance of the block rather than existing as separate objects. If you chose the Retain radio button, the objects remain in place but aren’t converted into a block insert — they stay individual objects with no connection to the new block definition. If you chose the Delete radio button, the objects disappear (but the block definition still gets created).

  You can include in a block definition a special kind of variable text object called an attribute definition. When you insert a block that contains one or more attribute definitions, AutoCAD prompts you to fill in values for the text fields. Attributes are useful for variable title block information (sheet number, sheet title, and so on) and symbols that contain different codes or call-outs. I describe how to create and use attribute definitions later in this chapter. 

BLOCK and WBLOCK

The Block command, which opens the Block Definition dialog box, is great for use within a drawing, but what if you want to use the block definition in multiple drawings? The easiest method is to use DesignCenter to copy a block definition from one drawing to another, as described in Chapter 4.

Another method involves the WBLOCK and Insert commands. I don’t cover this method here, because it’s less intuitive than using DesignCenter. But you may hear AutoCAD drafters talk about “wblocking” part of a drawing. So that you can keep these block-y names straight:

? The Block command creates a block definition from objects in the current drawing.

? The WBLOCK command creates a new DWG file from objects in the current drawing, or from a block definition in the current drawing.

  Keep your common symbol drawings in one or more specific folders that you set aside just for that purpose. You may want use one of the following techniques to develop a block library of symbols that you use frequently:

? Create a separate DWG file for each symbol (using WBLOCK, or simply by drawing each one in a new drawing).

? Store a bunch of symbols as block definitions in one drawing and use DesignCenter to import block definitions from this drawing when you need them.

Inserting blocks

AutoCAD provides a number of ways to insert a block, but the most commonly used and most flexible is the Insert dialog box. Here’s the procedure for inserting a block: 

1. Set an appropriate layer current, as described in Chapter 4.

It’s a good idea to insert each block on a layer that has something to do with its geometry or purpose:

 • If all the objects in the block definition reside on one layer, then it’s usually best to insert the block on that layer.

 • If the block geometry spans several layers, choose one of them to insert the block on.

  If any of the block definition’s geometry was created on layer 0, then that geometry will inherit the color, linetype, and other object properties of the layer that you insert the block on. It’s