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An expansion anchor serves as an alternate to traditional screws or nails when fastening an object to the wall, floor, or ceiling. Designed for use in solid materials, expansion anchors are often used in wood or masonry to ensure a secure and solid bond. The ends of these anchors expand during installation to grip the surrounding surface, which prevents the anchor from slipping out of the opening.
Builders and homeowners may use an expansion anchor to fasten a picture to the wall, or to hang a flowerpot from the ceiling. These anchors may also be used to secure objects to floors or outdoor paved areas. While the expansion anchor is often associated with concrete or masonry applications, it's also commonly used in wood and even drywall.
For applications involving drywall or wood, a plastic expansion anchor may be sufficient. These anchors consist of a plastic casing with wings at the tips. The installer drills a hole in the wall then presses the anchor in place by hand until the head is flush with the wall. When a nail or screw is inserted into the center of the anchor, it forces the wings at the end of the casing to spread out to the sides. These wings, or fins, are then able to grasp the drywall or wood from many different angles to hold an object in place.
Metal expansion anchors are typically required to join objects in concrete or masonry. These bolts consist of a steel casing with fins at one end, and a standard screw inserted in the center of the casing. Installers start by drilling a hole, then insert the bolt by hand. Once the bolt is in place, a screwdriver or drill is used to tighten the screw. This pulls the screw up inside the fins of the bolt, forcing these fins out to the sides.
Both double and single expansion anchor models are available to suit the needs of various applications. Single expansion bolts have fins at one end, while double expansion bolts have fins at both ends. Double-ended expansion anchors work well in fragile materials, such as soft stone or mortar.
Users should keep in mind that an expansion anchor is only as strong as the material in which it is installed. This means that an expansion anchor will not hold if the surrounding surface is weak or badly damaged. Expansion anchors may not be suitable for use in damaged or crumbling concrete or softer woods.