BLOCKTOXREF command
Replaces all instances of a block with an Xref.

Icon:
Method
Select one or more block references to replace with Xref/s.
This command displays the Block to Xref dialog box.
Note: The block name for the Xref is generated from the file name. If an Xref (or
overlay) with the same name already exists in the drawing, the block is replaced
using existing Xref.