folding spring anchor dowel made of steel with tip in form of a half-ring for screwing in materials with empty space,

anchor automatic background ceiling chandelier construction cornice dowel drilling drywall empty fix fixing folding form galvanized gray grip halfring hole hollow hook iron isolated locking lying made materials mechanism metal mount nut plate reliable ring rod screw screwing shadow shadows shelf space spring steel sticking support surface suspended thread tip unfold washer white wings woodfiber