Tap the door with your knuckles. If it makes a deep sound then it is probably hollow and you need to use hollow wall anchors to secure the fixing screws. If the door is solid then you will not require these.
Measure the width of the door using the tape measure. Divide this number by two to find the middle point. Measure across the door to the middle point and make a spot with a pencil.
Hold a spirit level vertically against the spot and draw a 6-inch line through the pencil mark. Measure the desired height for the hook from the bottom of the door and draw a 2-inch pencil line horizontally through the first line.
Hold the hook against the door to center it over the pencil cross. Push the tip of the pencil through the hook's fixing holes to mark their position on the door.
Drill holes in the door using a No. 6 drill bit at the pencil points. Do not drill any holes if you are working with a solid door. Hollow doors have a skin around 1/8-inch thick, so drill only through the skin the hook is to be mounted upon. If your drill has a depth guide, set it to 1/4 inch.
Insert No. 6 hollow wall anchors into the drilled holes. Use a rubber mallet to tap them flush to the surface of the door. Hold up the hook and affix it to the door using 1/2-inch No. 6 screws. For a solid door use 1/2-inch self-tapping screws and drive them in with an electric screwdriver. Erase any pencil lines still visible.