This is, actually, four separate pieces. The leveling base with a 3/8th tripod screw at the top, which has a rounded bottom that sets into a bowl shaped insert that is bolted into the center of the tripod frame that the tripod legs are attached to. Three hex head bolts securely attach the insert into the center of the tripod frame. You can see the hole for one bolt on the left side of the insert. The next bit is the small locking collar between the bottom of the insert and the handle. The collar slips over a large bolt, about 15mm in diameter that extends from the top of the handle, thru the collar and the insert and threads into the center of the rounded bottom of the base.
When assembled, everything remains aligned along the centerline of the handle and the 3/8ths diameter bolt threaded into the camera base except for the leveling base, itself. You turn the handle to loosen the assembly and this allows everything to swivel, universally, at an angle of up to about 20 degrees relative to the leveling base. Tightening the handle, which is nice and large, with large, deep grooves making it possible to get a good grip, allows you to clamp everything in position at whatever angle you want within the 20 degree arc that it is capable of.
In use, it is not practical to thread the camera onto the base. It is much easier to unscrew the handle and remove everything from the tripod insert. You thread the 3/8ths mounting bolt into the camera base and tighten the leveling base to the camera. With the leveling base securely tightened onto the camera base, you set the base into the tripod insert and then, from beneath, thread the handle with the locking collar back up, into the leveling base and tighten to hold everything in position. It sounds more complicated than it is.
For carrying everything, keep the base attached to the camera with the insert bolted into the tripod. That leaves only the handle and locking collar loose to keep track of. The handle and collar go into your pocket. This allows you, for short distances, to balance the load with the camera in one hand and the tripod and a bag of film holders and stuff in the other.
Setting up, using the camera levels, is no more difficult than using a ball head, it just does not provide as much leeway in positioning the camera and it does not allow panning the camera with everything else held constant. If you must pan the camera, without allowing any other movement, Feisol makes a panning base that looks like it could be placed between the leveling base and the camera to make that possible.
The leveling base with the Feisol CT-3371 tripod makes a very rigid, but light-weight means of providing adequate control and support for my 8x10 camera. I wonít say that it is as stable as a Linhof Profi III tripod and head, nor does it provide that kind of control, however, the Feisol set-up weighs less than 7 pounds where the Linhof tripod and head weigh, together, about 22 pounds. Setting the camera up with a 24 inch Artar focused at infinity and attaching a laser alignment tool, I donít see much more deflection using the Feisol than I do with the Linhof. No, the Feisol is not the equal of the Linhof for stability and control, but it is more than adequate for what I am using it for.