The user may specify one or more clashes which, although real interferences, are to be omitted from subsequent clash reports. Such clashes are referred to as approved clashes.

The obstruction limits boxes for all approved clashes, as represented in the spatial map, are identified in a separate list known as the approval list. This enables the program to check which items have been moved within the design after approval, and therefore to alert the user to the fact that some clash approvals may no longer be valid.