Protective system
Protective system means a method of protecting employees from cave-ins, from material that could fall or roll from an excavation face or into an excavation, or from the collapse of adjacent structures. Protective systems include support systems, sloping and benching systems, shield systems, and other systems that provide the necessary protection.
Source
29 CFR § 1926.650
Scoping language
Scope and application. This subpart applies to all open excavations made in the earth's surface. Excavations are defined to include trenches.