1. Generally speaking, the wooden keel is about 1.1 meters per square meter, because the size of plywood or gypsum board is 1.22 meters * 2.44 meters, and the wooden keels are usually beaten into 300*300 lattice. 2. Pull the thread (cement rope or fish wire) between the two ends and tighten the thread to see if it is flat. Plastic water pipes are used to set the level water line. After setting the level water line, you can determine whether the two ends of the ceiling are the same height. 3. Make the shelf first and then raise it to fix it. 4. Wooden wedges. 5. Level the water, use 6cm expansion screws to fix the 5*3 wooden keel to the bottom of the original ceiling (the distance is about 1.2 meters), connect the 2*3 wooden square to the 3*5 wooden square (the length is slightly lower than the ceiling), and install For the wooden keel frame, connect the shelf to the 2*3 wooden squares hanging from the ceiling, adjust the level, cut off the part of the hanging wooden square that protrudes from the keel frame, and seal the gypsum board. The previous method was to use the beams at both ends of the whole fir house or make false beams on the wall. Now most of the time, 6cm expansion screws are used to fix the 5*3 wooden squares to the cement ceiling to make small false beams to fix the hanging ones. Small wooden square.