Pick the rail and the exact face where the accessory will sit. Note whether it runs horizontally or vertically, and check that you can reach the part from the seat. The same rail can give you different clearances on each face.
Measure the rail and check the slot
Measure across the two faces at the end of the extrusion, or look up the cross section in the rig’s manual. A 4040 profile is nominally 40 by 40 mm. A 4080 profile is 40 by 80 mm. Those numbers describe the outside dimensions. Use the manufacturer’s slot specification to check the slot opening, the cavity behind it, and the distance between slot centers if the bracket spans two slots.
Check whether the T-nut slides in from the end of the rail or drops into the face. A seat upright or end cap can block access to the end. Follow the hardware maker’s instructions and make sure the nut seats before tightening.
Check the mount against the hardware
For a wheel mount, match the quick release as well as the rail. Our Fanatec QR2 rig mount lists 8040 profile fit and includes two M6 × 14 mm screws and two T-nuts. The cable management clip lists 8020 and 8040 profile fit and locks into the side slot with a quarter turn. The two parts use different ways to attach to the rig.
Check clearance before tightening
Set the bracket in place and check that it can sit flat. Try the intended seat position and make sure the bracket clears sliders, other controls, and cables. For seats, screens, and wheelbases, follow the equipment maker’s hardware and tightening instructions.
If the rail or slot is hard to identify, send us the rig model and a photo showing the slot and where you want to mount the part.