[University of Illinois] A shield to prevent tripping of some
Big Red Switch by clumsy or ignorant hands.
Originally used of the plexiglass covers improvised for the BRS on an IBM
4341 after a programmer's toddler daughter (named Molly) frobbed it twice
in one day. Later generalized to covers over stop/reset switches on disk
drives and networking equipment. In hardware catalogues, you'll see the
much less interesting description guarded button
.