Bolt free invasive, not use gas cutting reaming, with cutter knife hole, the holes need to make amendments lamellar close to prevent iron into joints and hole cutter wheel machine after use to remove the burr hole, and to remove iron.

• 螺栓不能自由穿入时；不得用气割扩孔；要用绞刀绞孔；修孔时需使板层紧贴；以防铁屑进入板缝；绞孔后要用砂轮机清除孔边毛刺；并清除铁屑.