Shoes / drums have either worn down, handbrake cable needs tightening slightly, or pistons are leaking into the drums.

you have to put your handbrake on and then it wont roll down the hill

does this happen when you want to reverse on a hill?, if so, the handbrake sensor thinks the car is slipping and keeps the handbrake engaged, so you need to manually release the handbrake by pulling it (exactly the same way as you engaged it)

Hope this helps

Robert

it has a sticky handbrake switch

Beeb the horn at grannies on the sidewalk. Let the handbrake off on a hill. Make faces out the rear window at the driver behind.