Use these measurements to mark the size of the doorframe opening on the slab door with a pencil. If your floor is carpeted, leave a 3⁄4 inch (1. 9 cm) clearance at the bottom of the door instead of a 1⁄8 inch (0. 32 cm) clearance. This will allow more room for the door to swing open without getting caught on the carpet. [2] X Research source When marking your measurements on the slab door with a pencil, use a ruler to make sure that you draw a straight line. This will allow you to make a clean, even cut when you plane or cut it down with a circular saw.

If the old and new slab doors are the same size, you can leave the new slab door as is. If the new slab door is longer or wider than the old door, use a pencil to trace the shape of the old door on the new slab door. [4] X Research source

If you are using both a new doorframe and a new slab door, attach the hinges so that the top hinge is 7 inches (18 cm) from the top of the door frame and the bottom hinge is 11 inches (28 cm) from the bottom of the door frame.

Repeat this process to cut the mortise for the other hinge.

If you need to buy the screws separately, bring the hinges with you to the store so you can make sure you get the right size.

Repurposed doors and some new slab doors may already have a hole cut for the doorknob. If this is the case, you can skip this step. 36 inches (91 cm) is the standard height for most doorknobs. You can adjust this, however, depending on your preference, as well as to suit the particular size of the door.

If you are using a repurposed slab door, you can either use the existing doorknob or replace the doorknob with the new one that fits into the existing holes.

If you are attaching your slab door to an existing doorframe, the mortises will already be cut and you can skip this step.

You may need to use wooden shims to help hold the door tightly into place while you drill the hinge screws into place.

While you can paint or stain the slab door before hanging it, you may end up scratching or chipping the paint during the process. Therefore, it could save you some time to do this at the end. [12] X Research source