Ball catches sit inside the top of the door and keep the door shut by a friction fit between the catch and the door jamb. The ball catch consists of a barrel that contains a spring-loaded ball that fits inside the door, with only the top of the ball exposed. Ball catches are used on interior doors, because they don't provide any real security, and they typically are used on double doors where both doors are frequently used.
Locate the spot where the ball catch will be installed on the top of the door. Measure in 5 cm (2 inches) from the edge of the door and make a mark. This mark should be centred between the front and back faces of the door.
Measure the width and height of the barrel of the ball catch.
Drill a hole centred on the location mark. The hole should be slightly deeper than the height of the ball catch. Be sure to use a drill bit that is as wide as the ball catch, usually 2.5 cm (1 inch).
Drop the ball catch in the hole and fasten the face plate to the top of the door with the provided screws.
Shut the door and make a mark on the upper door jamb directly over the centre of the ball catch. Make a second mark on the under side of the door jamb that marks the centre of the door jamb, as measured from the front face of the door jamb to the door stop. This will centre the catch plate over the ball catch.
Drill a shallow hole centred on the mark on the underside of the door jamb. Use a drill bit that is 6 mm (1/4 inch) wider than the bit used to drill the hole for the ball catch.
Install the catch plate on the door jamb. The indention on the plate should fit into the shallow hole. Fasten the plate using the provided screws.
Adjust the ball catch up or down as needed by turning the ring located directly beneath the ball. Use a flat-bladed screwdriver to turn the ring. Insert a corner of the screwdriver blade in the notch in the ring, and push it to turn the ring. The door should close without requiring much pressure, and should stay closed without rattling around. Keep adjusting the ball catch until the door closes satisfactorily.