Kicking the Tires to check for pressure is the same as slapping the Hood to check for Fluids.

Check for the 5th Wheel pin to have possibly been pulled by some prankster BEFORE pulling away from a parking slot because one never knows who is doing what where. Quite many Drivers have dropped their trailers because they were in a hurry and their "friends" were laughing hysterically.
Check the Glad Hands because even though they shall appear to be hooked up, People have tricked Drivers by placing a small coin or slug between the seals thereby depriving the Air from its full journey. This has been and continues to be a hilarious approach to the Driver that is in a hurry.
Also watch out that some Joker doesn't SWITCH the Air Lines because then nothing releases the way it is designed to perform and one can spend a lot of time looking for the problem much to the joy of others.

There are many pranks that can be played out on the unsuspecting Driver.

DRIVER BEWARE=DRIVER BE AWARE!!