The double expansion anchor consists of four parts-- a two-piece tubular shield, a hollow, wedge-shaped cone and a wedge-shaped nut-- brought together into a single anchor unit. The shields are connected by a pair of spring bands. At one end is the nut and at the other the cone, each designed so as to not turn during expansion.
Double expansion anchors are used in soft masonry with machine screws or machine bolts which are exposed to vibration or side pressure. As the double expansion anchor sets, the opposite ends pull towards each other causing the elongation of the anchor body. The double expansion anchor doesn't fracture and allows for a fastening of any length. Can also be used in harder materials, including stone, brick, concrete or block