The third stage is the formwork.

The third stage is the formwork. You need a certain number of sheets of plywood or any other boards. For these purposes, mainly used waterproof plywood, which can be used several times. Thus, plywood is fixed around the perimeter of the trench under the foundation above the ground at least 40 inches. Between themselves, the sheets are attached by reinforcement, which is cut off when dismantling after pouring.