Joints
From Legacy Roblox Wiki
A joint, called a "connection" while a game is loading, is something that connects two parts together. Common types of joints are Welds, Snaps, and Hinges. Joints are represented using a JointInstance object, which has four important properties: C0, C1, Part0, and Part1.
Automatic creation
How joints work
weld.Part1.CFrame == weld.Part0.CFrame * weld.C0 * weld.C1:inverse()
