The Manfrotto 577 Rapid Connect Adapter gives you the freedom to
remove the camera from the head without detaching it from the plate. It
includes the 501PL plate and is compatible with the 501PLONG camera
plate as well. A 1/4"-20 screw and a 3/8"-16 screw are included so you
can use the plate with various cameras. Corresponding threaded holes on
the side of the adapter allow you to store the screw that is not being
used, so you can access it if and when you need it.