Drop-in anchors are threaded metal sleeves that slide into a pre-drilled hole, to anchor or fasten a structure to concrete. Once the anchor is installed, a bolt can be dropped into the anchor and tightened. No nut required. These type anchors are used in running cable wires, HVAC ductwork, and fire sprinkler pipes. Zoro also has a super selection of sleeve anchors and anchor bolts too.