The other requirement specified in

The other requirement specified in the condition covering remote mirrors is that the mounting must be secure. This covers two concerns. First, the mounting must be a sturdy design that provides for a very positive locking of the mirror's orientation. Second, there must be adequate protection in the context of the specific show or display to prevent accidental misalignment of the mirrors by someone bumping into them or dropping something on them. In some situations, there may have to be beam containment enclosures or baffles to prevent a beam from a misaligned mirror from entering audience areas. The Center's concern for adequate protection from accidental mirror misalignment increases when the beams have a long projection range and the allowable angular deviation is quite small.