New attributes assigned to existing block references use their default values. Old
attributes in the new block definition retain their old values. Any old attributes
that are not included in the new block definition are deleted.

The following prompts are displayed.

Name of block you wish to define

Specifies the name of the block whose definition you are modifying.

Objects for new block

Specifies the objects to be included in the new block definition. Select the objects.

Insertion base point for new block

Specify the location of the block base point.