Horseshoe button play: make two dead buttons at the top of the online group, one big and one small. When the connecting rod is slightly pulled out from the middle of the big buckle to form a horseshoe buckle, it is sleeved on the slightly red rope of the rod and then tightened. The knot is getting tighter and tighter, so don't worry that it won't untie. It's very convenient to just pull the small button when you untie it.