When two plates are welded together at a split knuckle, the butt weld rules must use the angle between the plates to calculate the bevel depths and angles. The same parameter rule may be used for a planar plate or a knuckled plate, but the rule should calculate the value differently for each case.
The following picture shows a knuckled plate that must maintain a bevel opening of 45 degrees. The CornerButtMountingAngle is used to calculate the adjusted bevel angles. Note that the CornerButtMountingAngle may be returned as shown in the following picture, or it may be the angle inside the knuckle; the calculations must check to see which angle has been returned.