The rack slots through the middle of the spare wheel and has a mounting plate attachment which bolts securely to the wheel fixture on the rear door. There are different mounting plates available (to match up to the different bolt hole configurations).
Adjustable offset allows for left, right or centrally positioned spare wheels.
The horizontal bar, which the bike rack arms sit in, can be adjusted according to the position of the spare wheel i.e. left, right or centre to ensure that the bike rack does not overhang the vehicle.