Duplicate Block Name Nightmare - AutoCAD Block inserts with mystery entities

This block snafu question was submitted to us by a busy CAD operator who was driven nuts by unwanted entities which mysteriously inserted with his titleblocks. It is a useful example of how not to setup office blocks.

1. Two titleblocks are created with 2 different names. The border is a another block inside each titleblock.

The 8.5x11 border block in the 8.5x11 titleblock has the same name (TB_BORDER) as the 11x17 border block (TB_BORDER) in the 11x17 titleblock.

2. The 11x17 title block looks fine. There is no sign of other block entities in the drawing. We don't see an addtional 8.5x11 border in this drawing.

3. If the 11x17 Title block is inserted into a drawing in which the definition of the 8.5x11 border block already exists we see an unwanted block entity - the 8.5x11 border. Note that the 11x17 border block was not pulled up by the drawing. The existing definition was used. This results in a corrupted title block. The end user may be clueless as to the cause.

4. To fix. Rename the internal TB_BORDER block. You can use the RENAME command without exploding the blocks.

5. If you need a fast temporary fix, attach the TitleBlock as an XREF .

Best Practices: Keep block names distinctive, descriptive and different for each entity in your block library. This includes blocks you are using to build other blocks.