Molly (fastener)

A molly or molly bolt (often misspelled moly[1]) is a type of screw fastener that fastens objects to plaster or gypsum board hollow walls by providing an anchor to be lodged inside a hole and expanded once in position.

Other names used for this same general type of fastener include hollow-wall anchor and hollow-door anchor, sometimes with design variations but always with the same design theme of expansion via deformation as the screw is tightened.

[3] Although his patent acknowledges that expandable fasteners of this general kind were already known, Croessant's patent is intended to provide "an improved and adequate anchoring grip that may be retightened if necessary and that will permit repeated withdrawals and reengagements of the associated bolt."

[1] The fastener is an anchor, an expandable sleeve that slides into a hole drilled into the wall.

A machine screw is screwed into the sleeve, causing the anchor to bend, expand, spread and grip against the inside of the hole or behind it (in hollow contexts such as drywall over stud cavities, or hollow doors).