Write Block

Unlike create block, write block enable you to write blocks outside the drawing
The simple way to start WBLOCK command, just input W

Source
Block: Select a block within the drawing
Entire drawing: Automatically select all objects within the drawing
Objects: Select objects to be convert to block

Destination
File name and path: The block saved location outside the drawing
Insert units: Change it if different from the default units

Write Entire drawing to block will clean up all unused named objects