Final answer:
Trench shields are engineering structures used to prevent cave-ins during excavation work.
Step-by-step explanation:
Trench shields are an engineering solution designed to prevent cave-ins during excavation work. They are large, sturdy structures made of metal or other materials that are placed around the sides of a trench to provide support and prevent the soil from collapsing inwards. Trench shields can be used in various construction projects, such as laying pipelines or building foundations.