Weifeng WT-531B Tripod Special PTZ Quick Release Plate It’s the top board that connects the camera to the tripod.
The quick release plate is an accessory that can mount the camera on a tripod in one step. Especially when multiple cameras are used on a tripod at the same time, it is much more convenient to install each camera on the quick release plate in advance, and then exchange the cameras.
1/4 screw interface:
Twist the lock knob by hand: