pro user Amber II Assembly Instruction And Safety Regulations page 35

Step 2
Parts
Mounting:
Slide the U-frame against the outside of the U-frame holders of the
base frame. Secure this U-frame with the supplied carriage bolts
(M8x60), washers and plastic rotary knobs.
Make sure the plastic rotary knobs are on the inside (see picture).
Please note: firmly tighten both rotary knobs so that the U-frame
will come on its place well.
Unscrew the plastic rotary knob of each frame
holder, so the clamps can be folded open. First
attach the rubber ring around the U-frame and
put the clamp around it. Subsequently, re-attach
the holder and screw the plastic rotary knob until
you can just turn the frame holders (the frames
of the bikes have to be attached to it, so they
have to be movable). The sides with the straps
are intended to fasten the bike.
End result:
35