These Molly Bolt Fasteners by Prime-Line Products are constructed of steel components, and they are used as specialized screws to fasten objects to plaster and gypsum board where there are hollow walls. These fasteners are anchors with expandable sleeves that slide into pre-drilled holes of hollow walls. A lip wider than the hole prevents the bolts from falling into the hole and behind the hollow walls. Upon fastening, a machine screw is then screwed into the sleeve, causing the anchor to bend, expand, spread and grip against the inside of the drywall. These fasteners fit into a 1/4in. diameter holes, and they will fit up to 9/16in. thick panels. Will self pierce into the desired surface.