Put a good door cover line into the doorway, with the back of the door cover line on the same parallel plane with the doorway, fix it down from the left and right sides of the doorway with wooden wedges, check the verticality of the door cover line with a hanging hammer, so that the verticality deviation is 65438 0 mm and the diagonal error is 3mm, and check the levelness of the horizontal cover plate with a spirit level, so that the levelness dimension is 65438 0 mm, and the levelness and verticality meet the requirements. Draw a mark with a pencil on the other corner of the L-shaped joint corresponding to the position of the round hole on the wall, and make corresponding marks on all joint positions. Take off the door cover line, put it aside, and drill a hole at the marked position on the wall with an impact drill. The hole diameter is ∮8 to ∮ 10mm, and the hole depth is 50 to 60 mm. When drilling, the impact drill bit is slightly inclined. Then put the newly removed door cover wire into the hole, adjust the levelness and verticality, slightly fix the door cover wire with a wood chipper to prevent shaking, and then fix it with a 30mm tapping screw on the other side of the L-shaped iron joint with a wood chipper (the screw must be tightened with a screwdriver or a speed-regulating electric drill, not directly knocked in with a woodworking hammer). If the gap between the door cover line and the wall is large, nail a circle around the hole first.