Closed sheeting uses vertical timber or metal members to cover and support a trench wall fully, braced by other parts of the support system (Figure 16). Side lacing, a type of closed sheeting, keeps soil from slipping by packing fill behind steel plates or timber boards; it works in all ground and is useful for long or large diameter pipes and variable ground where other supports are hard to fit, and it should be firmly wedged so it does not shift when fill is placed. Where these methods are used against collapse, workers should not go into the excavation before the sheeting or lacing is installed or after it is removed, should not work in the trench outside its protection, and should enter a sheeted or laced area only by ladder.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.