Anchor bolts are used in difficult applications, such as concrete and hollow walls. Expansion anchor bolts are used in solid walls or floors. These bolts anchor by expanding when a screw or bolt is threaded into the hollow shaft. Expansion anchors are made of plastic or lead. Lead anchors are used in concrete. Hollow-wall anchor bolts come in a variety of styles: Threaded drywall anchors, threaded drywall toggles, winged plastic anchors, toggle bolts, and a sleeve-type hollow-wall anchor called a "Molly."
Calculate the strength of the anchor bolt needed for your project. Factors affecting strength include the weight to be supported, the pull-down force and the temperature to which the bolt will be exposed. There are different types of anchor bolts for various applications. (See Resources 1, 2 and 3.)
Match the anchor bolt to the project.
Make a hole in the wall or floor with a drill or awl. An awl is preferable in drywall to avoid dulling your drill bit. A masonry bit, however, is necessary for installing anchor bolts in concrete, brick or other masonry. In drywall or wall, the hole should be slightly smaller than the anchor bolt.
Tap the bolt into place with your hammer. The anchor bolt should fit snugly in place.
Turn the anchor bolt screw into the threaded shaft to tighten the bolt in place. The wings or mollies, depending upon the type of anchor bolt used, will expand and release, creating wings inside drywall and preventing the bolt from coming out.
The toggle anchor bolts that come with towel rods and other kitchen and bath accessories may not be as large as needed to bear the weight to which the rod will be subjected. Purchase larger toggle bolts to ensure long and satisfactory service.
Anchor bolt epoxy may be used for greater strength for anchors in concrete or masonry. Follow epoxy manufacturer's instructions carefully. The drilled hole must be clean and free of dust for bonding of epoxy to the masonry and bolt shaft.