 If any cans stick above the level plane they can be flattened to the desired height.Nails and lath sticking out from under the window frame holds the bottom of it in place, and the sides and top of the frame are fastened in the same fashion as a door frame.To make a smooth transition from door (or window frame) to tin can wall with plaster, sheets of metal lath are attached to the rim of the frame and folded over the gap between the frame and the can wall.