Shield anchors (frequently referred to by the historical brand name Rawlbolts) are heavy-duty, torque-controlled expansion fixings configured for medium-to-heavy applications in concrete, solid brick, and hard natural stone.
They feature an exceptionally thick, three-piece segmented outer shell (the shield) held together by a small metal spring or band.
Because the shield walls are much thicker than those of standard sleeve anchors, they provide a massive radial expansion force.
This makes them highly effective in older masonry or slightly oversized holes where weaker materials might otherwise crumble.
Core Mechanics & Structural Varieties
A shield anchor works via an internal, wedge-shaped tapered nut resting at the bottom of the segmented casing. As the bolt is turned and tightened from the outside, it draws the wedge nut up into the core of the anchor. This mechanical draw forces the thick metal interlocking wings of the shield outwards, embedding them deep into the surrounding substrate.
Unlike other single-purpose anchors, shield segments are highly customisable and accept various attachments:
- Loose Bolt Type: Features a standard removable hex head bolt. Ideal for fixtures that might need to be taken down or serviced later, as the bolt can be completely extracted while leaving the shield flush in the wall.
- Projecting Bolt Type: Utilises a fixed external threaded stud that projects outwards out of the wall, secured by a separate nut and washer. Perfect for hanging exceptionally heavy brackets because you can rest the weight of the metal plate onto the studs before threading the nuts on.
- Hook / Eye Bolt Type: Fitted with a forged open hook or closed ring loop. They are extensively used for anchoring tensioning wires, catenary cables, and overhead support chains.
- Shield Only: The empty expanding shell can be bought standalone, allowing engineers to integrate custom lengths of high-tensile metric threaded bars or bespoke security fasteners.
Drill Bit Sizing Discrepancies
Because the protective interlocking shield walls are remarkably thick, the required drill bit diameter is significantly wider than the bolt thread size.
