In Roblox programming, what constraint are welds subject to?

Welds are used for things such as car, trucks, buses, trains and etc

welds are a type of JointInstance that rigidly holds their parent part and another part in a fixed position relative to each other, such as holding one part 2 units to the right of another part. They can be used in places where parts need to be held together at odd angles, but still be able to move (meaning they will not work with BasePart. Anchored parts), such as for a vehicle.