Wooden plug for protection of deep foundation excavation pit

Protection of horizontal excavation pit of a 35 cm diameter pile, until it is concreted, made by wooden planks of 20x7.2 cm pine, placed one next to the other to cover the entire pit, reinforced at the bottom by small planks nailed in the opposite direction, with a rebate in the reinforcement to accommodate it in the pit so that it prevents horizontal movement, prepared to withstand a point load of 3 kN. Reusable 4 times.