The VariZoom Quick-Release Camera Plate with a 15mm Rod is designed to attach atop a VariZoom 15mm Adjustable Clamp, which is sold separately.
The plate assembly has a locking mechanism that prevents the top plate from accidentally sliding off. Upon the press and hold of a red button on the side of the assembly, the plate can be pulled out. On the other side of the assembly is a tightening knob that firmly tightens to keep the top plate from moving at all.
The top plate has a 1/4"-20 screw, and the bottom plate has underneath it a 1/4"-20 screw port that can be used if the attached rod is ever removed.