I'm not sure I totally follow the question, but:
There is a metal band attached to the heel binding (that sticks out forward), and a metal band connected to the toe binding (which sticks out backwards). These are firmly attached to the heel and toe binding, and don't need to come loose from them. As you probably know, the heel binding slides in a heel track, and the toe binding (if the Variozone lever in front is pushed to the side) slides in a toe track.
When the binding is mounted, the two metal bands are locked together with the "Xeed" screw (that's what my instructions call it anyway), which also holds down the plastic cover plate.
When the binding isn't mounted, the metal bands aren't connected together.
The main things you do when you mount the binding are:*
- Attach toe track (with toe binding in it) to riser/ski.
- Attach heel track (with heel binding it it) to riser/ski.
- Attach toe and heel bindings to each other with metal bands.
Don't do the last step until you've done the first two.
Okay so far?
A detail which might by stymieing you:
You should be able to get at the mounting screws for the heel unit (the screws that fasten the heel track to the riser/ski) by sliding the heel binding backwards. There should be two semi-circular "bites" taken out on either side of the heel's metal band ... line these up above the mounting screws to get full access to the screws.
Also: you don't need to take the bindings all the way out of the tracks to attach the tracks to the riser/ski. The instructions tell you to do it with bindings in the tracks, which is the only way I've done it.
One more possibly irrelevant detail: Use a #3 Pozidrive screwdriver.
*These aren't supposed to be complete instructions ... there are other details ... just a sort of big-picture schematic overview.