Trench shield

Structure used to prevent a cave-in of a trench

Trench shields are steel or aluminum structures used to avoid cave-ins and protect utility workers while performing their duties within a trench. They are customarily constructed with sidewalls of varying thicknesses held apart by steel or aluminum spreaders. Spreaders can be interchanged to match the width of the trench. The different materials and building designs lead to a variety of depth ratings: the depth of a trench that the shield can withstand a collapse without buckling. Depth ratings are determined by registered professional engineers.

This keyword could refer to multiple things. Here are some suggestions: