The lap joint flange is almost identical to a slip-on flange except for the radius at the intersection of the bore and flange face. This radius is necessary to accommodate connection to a lap joint stub end.

.Normally, a lap joint flange and a lap joint stub end assembly are used mainly in piping systems that are frequently dismantled for inspection or cleaning.

These flanges are advantageous in systems where the ability to swivel flanges and align bolt holes simplifies the erection of large diameter and hard-to adjust piping.