In the field of construction engineering, scaffolding is widely used and indispensable. Its stability directly affects the safety of construction personnel. In order to ensure a solid connection between steel pipe scaffolds, we usually use a tool called fastener. There are many types of fasteners, including double coupler (also known as cross coupler or directional coupler), swivel coupler (movable fasteners or universal fasteners), and joint pin coupler (straight fasteners or direct fasteners)