Modifying a Block

Modifying a Block
You can modify a block in two ways. One way is to completely redefine the block. In earlier versions
of AutoCAD, this was the only way to make changes to a block. A second way is to use the
Block Editor.
In this chapter, you’ll learn how to redefine a block by making changes to the door symbol.
Later, in Chapter 17, you’ll see how the Block Editor lets you add adjustability to blocks.
TIP Double-clicking most objects displays the Properties palette. Double-clicking a block opens
the Edit Block Definition dialog box, which gives you another way to edit blocks. You’ll learn
more about the Edit Block Definition dialog box in Chapter 17.

Unblocking and Redefining a Block
One way to modify a block is to break it down into its components, edit them, and then turn them
back into a block. This is called redefining a block. If you redefine a block that has been inserted in
a drawing, each occurrence of that block in the current file changes to reflect the new block definition.
You can use this block-redefinition feature to make rapid changes to a design.
To separate a block into its components, use the Explode command:
1. Choose Explode from the Modify toolbar. You can also type X↵ to start the Explode
command.
2. Click the door, and press ↵ to confirm your selection.
TIP You can simultaneously insert and explode a block by clicking the Explode check box in the
lower-left corner of the Insert dialog box.
Now, you can edit the individual objects that make up the door, if you desire. In this case, you
want to change only the door’s insertion point because you’ve already made it a more convenient
size. You’ll turn the door back into a block, this time using the door’s lower-left corner for its insertion
base point:
1. In the Draw toolbar, select Make Block, or type B↵. You can also choose Draw  Block  Make.
2. In the Block Definition dialog box, select Door from the Name drop-down list.
3. Click the Pick Point button, and pick the lower-left corner of the door.
4. Click the Select Objects button, and select the components of the door. Press ↵ when you’ve
finished making your selection.
5. Select the Convert To Block option in the Objects group to automatically convert the selected
objects in the drawing into a block.
6. Select Inches from the Block Unit drop-down list, and then enter Standard door in the
Description box.
7. Click OK. You see a warning message that reads “Door is already defined. Do you want to
redefine it?” You don’t want to redefine an existing block accidentally. In this case, you
know you want to redefine the door, so click the Yes button to proceed.
TIP The Select Objects and Pick Point buttons appear in other dialog boxes. Make note of their
appearance, and remember that when you select them, the dialog box temporarily closes to let
you select points or objects and otherwise perform operations that require a clear view of the
drawing area.
In step 7, you received a warning message that you were about to redefine the existing Door
block. But originally, you inserted the door as a file, not as a block. Whenever you insert a drawing
file by using the Insert Block tool, the inserted drawing automatically becomes a block in the current
drawing. When you redefine a block, however, you don’t affect the drawing file you imported.
AutoCAD changes only the block in the current file.
You’ve just redefined the door block. Now, place the door in the wall of the room:
1. Choose Erase from the Modify toolbar, and then click the door. Notice that the entire door
is one object instead of individual lines and an arc. Had you not selected the Convert To
Block option in step 5 of the previous exercise, the components of the block would have
remained individual objects.
2. Insert the door block again by using the Insert Block tool in the Draw toolbar or by choosing
Insert  Block. This time, use the Nearest Osnap override, and pick a point on the right-side wall
of the bathroom, near coordinate 9´-4˝,2´-1˝. Metric users should insert the door near 284,63.4.
3. Use the Grips feature to mirror the door, using the wall as the mirror axis so that the door is
inside the room. Your drawing will look like Figure 4.7.


TIP To mirror an object using grips, first be sure the Grips feature is on. (It’s usually on by default.)
Select the objects to mirror, click a grip, and right-click. Select Mirror from the shortcut menu;
then, indicate a mirror axis with the cursor.
Next, you’ll see how you can update an external file with a redefined block.