Shoring refers to the installation of a support system for trench sides in order to prevent soil movement, underground utilities, highways, and foundations. When the position or depth of the incision makes sloping back to the maximum permissible slope impossible, shoring or shielding is utilized. Sloping back means that as you dig down the side of the trench will become less steep until it becomes level with the bottom of the trench. This allows any water that enters the trench to flow out of the trench rather than pooling against the wall. There are several different methods used for shoring trenches. The simplest method is to use wooden stakes to hold back the earth. As the ground is moved away from the stake it can be replaced by setting another stake into the ground next to the first one. This process continues all the way along the side of the trench until there are no more stakes reachable without piling up the dirt beyond what can be removed by hand. The second method uses metal frames covered with plastic sheeting. These are attached to the face of the bank with bolts or nails. As soil is removed it is placed on top of the plastic sheeting which prevents it from falling into the trench. Once the trench has been excavated to its final width and depth the shoring is removed, leaving an open hole behind it. Trenches dug with this method can be refilled and re-excavated if necessary.