Trench box

A trench box, sometimes called a drag box or trench shield, is a welded steel box made up of two side panels held apart by adjustable spreader bars that is lowered into a trench to create a safe working chamber for engineers. The box does not retain the trench walls in the same way as full shoring, but creates a protected area within which work can be carried out safely. Operators must be trained on safe installation, use, dragging and removal of the box under PUWER 1998, LOLER 1998 and CDM 2015. Lifting eyes must be subject to thorough examination under LOLER. The technique is widely used on Thames Water adopted sewer replacement schemes in Greater London, where short connections to mainline drains are needed and full shoring would be impractical.