The Zacuto Blackmagic Top Handle for Blackmagic Cinema Camera, additional to outfitting the Blackmagic camera with a Handle for low shots and carry, also very usefully lets you slide the Handle sideways along five inches and to tighten it in the position where you find balance to be best. Five inches is how wide the Z-Rail is, and the Z-Rail is what the whole assembly attaches to the camera by -- the Handle attaches to the Z-Rail, and the Z-Rail attaches to the camera by means of two 1/4"-20 screws, which come included.
The Handle attaches to (and removes from) the Z-Rail by quick-release lever and can be attached facing front or back. Along its height are screw-holes for adding various accessories. And running through it is a 15mm rod threaded for more accessories. It's threaded on both of its ends to accept rod extensions or various compatible additions, such as Zacuto's T-Mount or Tri-Mount.