Original Message

Parking brake is powered by the auxiliary hydraulic system which has two reservoirs. They supply pressure for parking brake.  If you don't remember that it must have been awhile since you've flown one. As for chocks, common scenario is to do full preflight,  pull the chocks and hop in to start and the air craft starts to roll. If parked on slope you have two options

leave chock in until started and some one else pull it

dont empty the aux system resevoirs