They should have a rubber padding that goes underneath. If you got genuine ones, there should also be pre-drilled holes and nuts and bolts that go through the wing. The padding keeps any foreign matter from getting underneath. If they aren't genuine, I'd suggest returning them and getting genuines. They are curved in the front and on the outer edge to match the wing top perfectly.
1st pl Nevada Trophy 2004 & 2003
Currently no Land Rover - may be hunting for a 109" soon. ;)
G550, 06 BMW GSA, 75 Norton Commando "ACE", 06 Ducati Paul Smart, 00 Aprilia RSVR, 73 Moto Guzzi V7s