[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".
[glossary]
[Reference(s) to this entry by made by: {Big Red Switch}{check}{scram switch}]