Simondo, I'll add an E...
Check you put the fin and the screwdriver in the car after taking it off the board to stack on the roof rack.
And F...
If you have nicely cut foam pads that sit on your roof rack, make sure that you take them off the rack and put them safely inside the car when not in use. Double check if you are borrowing someone else's car and/or rack pads. (Jonathan, we need to talk)