You can create a block as a separate drawing file that you can insert into other drawings.
To save a block as a separate drawing file
On the command line, type wblock.
In the source tab, choose one of the following:
Block This option saves existing block object to a separate drawing file. When prompted, select an existing block name from the pull down menu of this option.
Entity drawing This option immediately saves the entire drawing to a separate drawing file.
Objects This option saves those objects you select to a separate drawing file. When prompted, specify the insertion point for the block, select the objects for the block.
In destination tab, type the name of the drawing file you want to create and choose the saved path.
NOTE When saving the entire drawing as a separate drawing file, the program assigns the 0,0,0 coordinate as the insertion base point. You can change the base point by opening the drawing and redefining the block.
Change the Base Point of Drawings to Be Used as Blocks
When inserting a drawing file into another drawing as a block, by default, system uses the origin (0,0,0) of WCS as the base insertion point. To specify different insertion point, you can use BASE command. Next time you insert the same block, system uses the new insertion point by default.
Update Changes in the Original Drawing
Once the drawing file has been inserted into another drawing as a block, the original drawing changes as well. But the block having been inserted will not change. If the block happens to change along with the original drawing, you should attach it as external reference but not as a block.
Use Paper Space Objects in Blocks
Objects created in paper space are not contained in the block when it is being inserted into the drawing. You can convert the objects in paper space as block or save as an individual drawing file before inserting into other drawings.
BASE: Sets the insertion base point for the current drawing
BLOCK: Creates a block definition from objects you select
EXPORT: Saves objects to other file formats
INSERT: Places a named block or drawing into the current drawing
OOPS: Restores erased objects
WBLOCK: Writes objects or a block to a new drawing file
System Variables Reference