Lap joint flange has a curved radius at the bore and face to accommodate a lap joint stub end. The lap joint flange and stub end assembly are normally used in systems requiring frequent dismantling for inspection. They are used on piping equipped with lap joint stub ends or with lapped pipe. These flanges slip over the pipe and bolting pressure is transmitted to the gasket by the pressure of the flange against the back of the pipe lap. Lap joint flanges have certain special advantages: freedom to swivel around the pipe facilitates the lining up of opposing flange bolt holes and the lack of contact with the fluid in the pipe often permits the use of inexpensive carbon steel flanges with corrosion resistant pipe or tubing. The stub is welded to the pipe and the lap joint then works as a backing ring. The main advantage of this type of flange is that the bolt holes can be aligned with the matching flange after the welds have been completed. They are primarily used on carbon or low alloy steel piping systems. They are also used in the erection of large diameter or hard-to-adjust piping configurations because of its quick bolt hole alignment.