Have you ever had to change a block and every instance of it in your drawing? The old tried and true way to do this was to explode the block, modify what you needed, purge the block and recreate it. Then the block definition changed, but the blocks in the drawing still looked the same as they did before you updated the block.
There is a better way now. Well, with 2008 and newer anyway. Enter the Block Editor.
- Select the block and type BEDIT (or double click the block).
- Click OK on the dialog that comes up after you verify your block is selected.
- Modify your block, say you want all the objects to be on a different layer. Select all and select another layer from the Layer dropdown list. Or you need to add a line, draw a line.
- Click the "Close block editor" button.
- Click Yes to save.
Now the objects are now on a different layer or you've added lines. Note: You have to explode the block to see that it actually changed the objects layer.
Ok, so it is Magic! :)
Note: this does not work when you try to add attributes. I believe BATTMAN can help though.