fuses

i have a few quick questions about fuses for my 2002 z71 lt extended cab. in my fuse box there are maxi fuses for post 1&2 and rap 2 and air. the a/c works fine without a fuse in air and everything seems to work like normal without a fuse in post 1 and rap2. i put fuses into these spots and didnt notice a change. i am just curious what these spots are for? thanks

Rap 2 may be window motor.
Stud 1 may be trailer wiring and level control.
The owners manual or fuse box cover under side should tell what is what.
MT