Creating a Symbol | Mastering AutoCAD 2005 and AutoCAD LT 2005

To save a drawing as a symbol, you use the Block tool. In word processors, the term block refers to a group of words or sentences selected for moving, saving, or deleting. You can copy a block of text elsewhere within the same file, to other files, or to a separate file on disk for future use. AutoCAD uses blocks in a similar fashion. Within a file, you can turn parts of your drawing into blocks that can be saved and recalled at any time. You can also use entire existing files as blocks.

On the CD You'll start by opening the file you worked on in the last chapter and selecting the objects that will become a block.

Start AutoCAD, and open the existing Bath file. Use the one you created in Chapter 3, or open 04-bath.dwg on the companion CD. Metric users can use the 04-bath-metric.dwg file. The drawing appears just as you left it in the last session.

Symbols for Projects Large and Small

A symbol library was a crucial part of the production of the San Francisco Main Library construction documents. Shown here is a portion of an AutoCAD floor plan of the library in which some typical symbols were used.

Notice the familiar door symbols, such as the door you created in Chapter 2. And, yes, there are even toilets in the lower half of the plan in the public restrooms. The method for drawing the wide flange demonstrated at the end of Chapter 3 is similar to the one that was used to create the I-beam column symbols shown here.

Symbol use isn't restricted to building components . Room number labels, diamond-shaped interior elevation reference symbols, and the hexagonal column grid symbols are all common to an architectural drawing, regardless of the project's size . As you work through this chapter, keep in mind that all the symbols used in the library drawing were created using the tools presented here.
In the Draw toolbar, click the Make Block tool or type B , the keyboard shortcut for the Make Block tool, to open the Block Definition dialog box. You can also choose Draw Block Make.
In the Name text box, type Toilet .
In the Base Point group, click the Pick Point button. This option enables you to select a base point for the block by using your cursor. (The insertion base point of a block is a point of reference on the block that is used like a grip.) When you've selected this option, the Block Definition dialog box temporarily disappears.

Tip
Notice that the Block Definition dialog box gives you the option to specify the X, Y, and Z coordinates for the base point, instead of selecting a point.
Using the Midpoint Osnap, pick the midpoint of the back of the toilet as the base point. Remember that you learned how to set up some Running Osnaps in Chapter 3; all you need to do is point to the midpoint of a line to display the Midpoint Osnap marker and then left- click your mouse.

After you've selected a point, the Block Definition dialog box reappears. Notice that the X, Y, and Z values in the Base Point group now display the coordinates of the point you picked. For two-dimensional drawings, the Z coordinate should remain at 0.

Next, you need to select the actual objects that you want as part of the block.

Click the Select Objects button in the Objects button group. Once again, the dialog box momentarily disappears. You now see the familiar object selection prompt in the Command window, and the cursor becomes an Object Selection cursor. Click a point below and to the left of the toilet. Then use a selection window to select the entire toilet. The toilet is now highlighted.

Warning

Make sure you use the Select Objects option in the Block Definition dialog box to select the objects you want to turn into a block. AutoCAD lets you create a block that contains no objects. If you try to proceed without selecting objects, you will get a warning message. This can cause some confusion and frustration, even for an experienced user .

Press to confirm your selection. The Block Definition dialog box appears again.
Select Inches from the Drag-And-Drop Units drop-down list. Metric users should select Centimeters.
Click the Description list box and enter Standard Toilet .
Make sure the Retain radio button in the Objects button group is selected and that the Create Icon From Block Geometry radio button is selected in the Preview Icon group, and then click OK. The toilet drawing is now a block with the name Toilet.
Repeat the blocking process for the tub, but this time use the upper-left corner of the tub as the insertion base point and give the block the name Tub. Enter Standard Tub for the description.

Tip
You can press or right-click the mouse and choose Repeat Make Block from the shortcut menu to start the Make Block tool again.

Restoring Objects That Have Been Removed by the Make Block Tool or the Block Command

Before AutoCAD 2000, Block was the only command available to create blocks. This is a command-line version of the Make Block tool and is still available to those users who are more comfortable entering commands via the keyboard. To use it, you enter the word Block preceded by a minus sign at the command prompt, as in “Block . When you use the Block command, the objects you turn into a block automatically disappear. AutoCAD's Block tool (Bmake) gives you the option of removing or maintaining the block's source objects by way of the Retain option, shown in step 5 of the preceding exercise.

If you use the Block command, or if for some reason you leave the Retain option unselected in the Block Definition dialog box, the source objects you select for the block disappear. You can restore the source by using the Oops command. You can also use Oops in any situation in which you want to restore an object you accidentally erased. To use it, simply type Oops in the Command window. The source objects reappear in their former condition and location, not as a block.

When you turn an object into a block, it is stored within the drawing file, ready to be recalled at any time. The block remains part of the drawing file even when you end the editing session. When you open the file again, the block will be available for your use. In addition, you can access blocks from other drawings by using the AutoCAD DesignCenter and the Tool palettes. You'll learn more about the DesignCenter and the Tool palettes in Chapter 21.

A block acts like a single object, even though it is really made up of several objects. One unique characteristic of a block is that when you modify a block, all instances of that block are updated to reflect the modifications. For example, if you insert several copies of the toilet into a drawing and then later decide the toilet needs to be of a different shape, you can edit the Toilet block, and all the other copies of the toilet are updated automatically.

You can modify a block in a number of ways after it has been created. In this chapter, you'll learn how to make simple changes to individual blocks by modifying the block's properties. For more detailed changes, you'll learn how to redefine a block after it has been created. Later, in Chapter 6, you'll learn how to use the Xref And Block Edit tool to make changes to blocks.

Understanding the Block Definition Dialog Box

The Block Definition dialog box offers several options that can help make the use of blocks easier. If you're interested in these options, take a moment to review the Block Definition dialog box as you read the descriptions of the dialog box options. Or if you prefer, you can continue with the tutorial and come back to this section later.

You've already seen how the Name option of the Block Definition dialog box lets you enter a name for your block. AutoCAD does not let you complete the block creation until you enter a name.

You've also seen how to select a base point for your block. The base point is like the grip of the block. It is the reference point you use when you insert the block back into the drawing. In the exercise, you used the Pick Point option to indicate a base point, but you also have the option to enter X, Y, and Z coordinates just below the Pick Point option. In most cases, however, you will want to use the Pick Point option to indicate a base point that is on or near the set of objects you are converting to a block.

The Objects button group of the Block Definition dialog box lets you select the objects that make up the block. You use the Select Objects button to visually select the objects you want to include in the block you are creating. The Quick Select button to the right of the Select Objects button lets you filter out objects based on their properties. You'll learn more about Quick Select in Chapter 12.

Other options in the Objects button group enable you to determine what to do with the objects you are selecting for your block. Here is a listing of the options and what they mean:

Retain Keeps the objects you select for your block as they are, unchanged.

Convert To Block Converts the objects you select into the block you are defining. It then acts like a single object after you've completed the Block command.

Delete Deletes the objects you selected for your block. This is what AutoCAD did in earlier versions. You might also notice that a warning message appears at the bottom of the Objects button group. This warning appears if you have not selected objects for the block. After you've selected objects, the warning changes to tell you how many objects you've selected.

Preview Icon Lets you control whether a preview image is stored with the block. This option was added in AutoCAD 2000 and lets you easily locate and identify blocks in a drawing. You can, for example, peek into another drawing file without opening the file, and browse through the blocks that are contained in that file.

Drag-And-Drop Units Lets you determine how the object is to be scaled when it is inserted into the drawing using the DesignCenter feature discussed in Chapter 21. By default, this value will be the same as the current drawing's insert value.

Description Lets you include a brief description or keyword for the block. This option is helpful when you need to find a specific block in a set of drawings. You'll learn more about searching for blocks later in this chapter and in Chapter 21.