When building the walls, we first make a frame of 2x4s to which we will attach plywood after setting the frame in place. Our frames were a tight fit (no doubt a sign of excellent craftsmanship) and needed a little persuasion to align neatly. Hammers were used to coax the frames into place, as was a crowbar. It turns out a crowbar is not just for wrecking things… the flat part of the curved side can also be used to tamp wall frames into place. After everything was square, the frames were affixed with a nail gun.