This spring wing toggle bolt, also known as a butterfly anchor, is a fastener for hanging items on hollow walls such as drywall. sping toggle bolts have wings that open inside a hollow wall, bracing against it to hold the fastener securely. The wings are much larger than the bolt they are attached to which spreads the weight of the secured item over a larger area. The item to be secured is preassembled onto the the bolt BEFORE the toggle is pushed into the plasterboard. They are used in a wide variety of domestic and commercial applications.