The full schnabel refers to the double gooseneck arrangement to grasp the load at both ends. The gooseneck towers have special hooks that cup the flange of the tower sections. The tower section is then used as a self-supporting structural member that links the front and rear half of the trailer configuration. This allows for the absolute lowest loading height possible.
The front and rear necks have secondary hook points that allow the two to be tied together for the return trip. The jeep can then be stacked on the dolly and rear neck. The front of the dolly is hung by the neck so it only rides on the last 3 axles.
The configuration shown is with a standard 2+1 jeep and modular dolly. These trailers can be replaced with other variations of themselves such as a 3 axle jeep and a 3+3 dolly. The combination of jeep and dolly becomes a client preference. They can be chosen with the lowest tare weight or the lowest loading height for eventual re-use for hauling beams or vessels.