I thought that all you experts out there would realise that most parking bays are built on an upslope of about 2%.
Why?
It makes it so much easier for the tug to push the aircraft back and it also makes it easier for those aircraft that are capable of doing so to power back by using reverse thrust without using a tug.
This has been discussed many times in the past on pprune (wake up those of you who are sat at the back of the class).