The Hinge Doctor HA3D by GKL Products is a specialized adjustment tool designed for commercial ball bearing hinges, particularly those measuring 5" × 5". It easily slips over the top hinge knuckle, allowing you to make hinge adjustments using a wrench—no removal required. Simply open the door slightly past the bind point, then remove the tool and repeat as needed until your door operates smoothly. This tool is especially useful for correcting sagging, dragging, or misaligned doors and stands out for its efficiency and ease of use.