Assemble your tools. To hang a slab door, you will need the actual door slab, doorknob, face plate, strike plate, and hinges. You will also need the following tools: hammer, nails, power drill with various bits, wood chisel, pry bar, speed square, spring clamps, and a pencil.
Match your new slab door to the one you are replacing. The fastest way to create mortises on your new slab door is to copy the configuration of the door you are replacing. Remove the doorknob in your old door and place the two doors side-by-side on the floor with their hinge sides pointing upward. If you like, you can clamp them together using spring clamps. This will keep them in place.
Use the speed square to mark your mortise cuttings. Take your speed square and pencil and copy the exact location and dimensions of your old door’s hinges onto the hinges of the new slab door. Measure from the top and bottom of the new door to make sure your markings are in the exact spot they need to be.
Use the chisel to cut out the proper space mortise. Make sure you use a sharp, high-quality chisel to do the most precise work possible. Make the mortise area as flat and smooth as possible.
Screw in the hinges. Using your power drill, remove the hinges from your old door and install them into your new door. To be on the safe side, you may want to drill pilot holes before moving on to the screws themselves. It is crucial that the hinges are flush with the side surface of the door. If they stick out too much, you will need to deepen your mortise. If they are too recessed, you will need to shim your mortise with either cardboard or a very thin strip of plywood. Once you’ve gotten your hinges completely flush, you’re ready to move on to the next step.
Hang the door. Place the slab door inside the doorframe. Use the pry bar to raise the door to the exact level of the existing drill holes on the door frame. When you have it perfectly lined up, drill the hinges into the existing holes. You must do this exactly right, or you’ll accidentally enlarge the door jamb’s drill holes and make the door unstable.
Install your remaining hardware. Once your door is hung, you can add remaining hardware like a doorknob and strike plate. Save this step for last because it’s a lot easier to tweak the positioning of a strike plate than the position of a hanging door.
