Replaces all instances of a specified block with a different block.
BLOCKREPLACE searches the entire drawing for a specified block and replaces it with another block that you specify. Afterwards, you can use the PURGE command to remove the unreferenced block definition from the drawing.
To use BLOCKREPLACE, click Tools -->Express Tools -->Replace Block...
Select the block to be replaced from the Select Original drop-down menu. Then select the block to be replaced with from the Replace With drop-down menu and click OK.
