Chapter 24 Standard Blocks 745 Copyright Goodheart-Willcox Co., Inc. the block. To create or update a block icon, open the drawing that contains the block, access the BLOCKICON command, enter the name of the block, and press [Enter]. Copying Nested Objects Some modify commands, such as TRIM and EXTEND, allow you to pick individual objects nested within a block reference or external reference (xref). However, most other commands recognize a block reference as a single block reference object and an xref as a single external reference object. For example, use the COPY command to create a copy of a block reference or xref. In contrast, the NCOPY command allows you to copy individual objects nested within a block reference or xref, which is more effi - cient than exploding a block and copying objects, for example. Access the NCOPY command and use the Settings option to specify the method for copying nested objects. The difference between the default Insert option and the Bind option is most apparent when you are copying named objects nested within an xref. Chapter 31 explains xrefs. Use the Insert option to copy objects nested within a block. Individually select objects nested within a block reference or xref to copy, specify a base point, and pick a location to place the copy. The Multiple option is avail- able before you specify a base point and allows you to create several copies of the same object using a single NCOPY operation. The NCOPY command provides the same options as the standard COPY command, allowing you to specify a base point and a Type BLOCKICON Type NCOPY Figure 24-13. A—The correct procedure for redefining a block. B—Redefining a block without first exploding it creates an invalid circular reference. B A BOX 1 block 1 circle BOX BOX BOX BOX BOX 1. Insert block 2. Explode block 4. Redefine (new definition) 4. Error (block references itself) 2. Edit block 3. Redefine attempted BOX redefined incorrectly Circle added 1. Insert block Circle added 3. Modify/add objects 4 lines Figure 24-14. The Rename dialog box allows you to change the name of blocks and other named objects. Select type of objects to rename Select block to rename New block name