Using External References

Using External References
AutoCAD allows you to import drawings in a way that keeps the imported drawing independent
from the current one. A drawing imported in this way is called an external reference (Xref). Unlike
drawings that have been imported as blocks, Xref files don’t become part of the drawing’s database.
Instead, they’re loaded along with the current file at startup time. It’s as if AutoCAD were opening
several drawings at once: the currently active file you specify when you start AutoCAD, and any
file inserted as an Xref.
If you keep Xref files independent from the current file, any changes you make to the Xref automatically
appear in the current file. You don’t have to update the Xref file manually as you do
blocks. For example, if you used Xref to insert the Unit file into the Plan file, and you later made
changes to the Unit file, you would see the new version of the Unit file in place of the old the next
time you opened the Plan file. If the Plan file was still open while edits were made, AutoCAD
would notify you that a change had been made to an Xref.
TIP You can’t Xref a file if the file has the same name as a block in the current drawing. If this situation
occurs, but you still need to use the file as an Xref, you can rename the block of the same
name by using the Rename command. You can also use Rename to change the name of various
objects and named elements. See Chapter 10.
Another advantage of Xref files is that because they don’t become part of a drawing’s database,
drawing size is kept to a minimum. This results in more efficient use of your hard disk space.
TIP Xref files, like blocks, can only be edited using special tools. You can, however, use osnaps to
snap to a location in an Xref file, or you can freeze or turn off the Xref file’s insertion layer to make
it invisible.