I have an exterior lock set with a knob on the inside. I can't get the interior doorknob off. It does not have a hole in the shaft of the knob in which you press a clip down to remove it. It's one of those where you pull the cover plate back away from the door and rotate an inner plate in the direction of the arrows. After I rotate the inner plate, what do I do next to remove the interior knob and the plate on the door. The interior plate is loose, so it seems to be out of its "Locked" position, but will not come off. I believe it's a Schlage lockset. It came with the house and is 22 years old.