How to remove standoffs in a computer case?

Im putting my motherboard into a new case and need the standoffs from my old case. but I dont know how to get them out. On the outside of the case they are hexagonal, and flush (flat) with the case, so i cannot use pliers to pull them out from the outside. on the inside of the case they stick out and have a screw hole in them. I guess I need to push them from the inside out, but i dont know how as they wont move if i try to twist, push pull...How to remove standoffs in a computer case?
Standoffs are almost always hexhead screws. Just use a pair of pliers and unscrew them. Only on one occasion did I ever see standoffs that were actually riveted to the motherboard tray.