The present invention relates to a vault door mechanism that assists a user in opening or closing the door. A hold-open arm and hinge plate pivotally interconnect the door to a surrounding frame and are fixed in place by an associated locking mechanism. The locking mechanism stops the door in the partially opened position prior to being fully opened or closed, thereby assisting the user in handling the door. The details of the present invention, and the manner in which they interrelate, will be described in greater detail hereinafter.