Round Head Toggle Bolts with Wings Strong hollow wall anchors that come with a machine bolt and a spring-wing to match. You need not to know the exact wall thickness with this anchor, it will adjust itself to almost any thickness depend-ing on the length of the bolt. These toggle bolts are made with standard round head machine screws. These are great in applications where a smaller diameter head is needed to fit into, between, or aside something, that the larger "truss head" might not