ManualWeld

An object that holds two parts together. It is commonly created when the Join Always setting in Studio is turned on.

Functions identically to Weld.

See also WeldConstraint for a newer alternative using the constraints system that does not require C0 or C1 properties to be manually set.

Root part

Every Assembly has a root part, see BasePart:GetRootPart(). When a ManualWeld's C0/C1 is modified the root part will stay where it was.

Directionality

ManualWelds do not have any directionality. Part0 or Part1, doesn't matter. You can imagine rigid joints forming a tree branching down from the root part. All the parts down the tree from root will move, and their welded "children" in this tree will move with them.