Once the concrete has gained sufficient strength, the tarps and heaters are removed, allowing the stripping to take place. The hy­draulic jacks that were used initially to raise the forms to the cor­rect elevation are reversed, pulling the forms away from the con­crete slab above. Also attached to the tunnel forms is a diagonal strut system that allows easy stripping of the forms from the walls and deck with one simple movement (see Figure 4.11). The forms can now be rolled away from the walls and hoisted away by crane to be cleaned and oiled in preparation for the next location.