A shelf rest (SRC) is a small clip that installs on the bracket tip to provide a stable contact point for glass shelves. Without a shelf rest, a glass shelf rests directly on bare metal — which can cause the glass to slide, rock, or scratch. Always use shelf rests (SRC) with rubber bumpers (SRB) when installing glass shelves on standard metal brackets. Alternatively, use the dedicated Glass Shelf Bracket series (GSB-Lrg, GSB-Med, GSB-SM, BRK-GLB) which include this protection built in.