Storage space, always a good thing, becomes even better when hidden. One way to do this is to build an access door into an area of the house that would otherwise be inaccessible. A dormer or false walls are examples of hide-able storage areas. Access doors also can be used to gain access to bathroom plumbing.
Locate the studs in the wall where the access door will be located. Measure up from the floor and make a mark at 24 inches. Place the carpenter's level on the mark and draw a horizontal line between the studs.
Place the framing square on the floor with the long edge of it going up the wall. Align it with edge of the stud and draw a line up the wall to the 24-inch line. Repeat this for the other stud.
Drill a hole in one corner directly beneath the horizontal line. Insert the saw and cut the horizontal line and then cut the two vertical lines. This should give you a hole measuring 14½ inches wide by 24 inches tall. Be certain the drywall is cut as close to the studs as possible. For an illustrated look on using a keyhole saw, see "Keyhole Saw" in the reference section of this article.
Cut the baseboard with a handsaw, if applicable. Place the door casing on a worktable. Set the electric miter saw on a 45-degree angle and cut both ends of the casing. Next, measure from the short point of each miter and make a mark at 24 inches. Set the electric miter saw on 0 degrees and cut the door casing on the 24-inch marks.
Place the 14½-inch 2 by 4 on the worktable. Drill two pilot holes on each end of the 2 by 4 at an angle with the drill and the 3/16-inch drill bit. Apply wood glue to the ends of the 14½-inch 2 by 4, place it behind the drywall between the studs and secure it with the drywall screws.
Place one of the pieces of door casing against the wall and align it with the stud. Place the carpenter's level against the outside edge of the door casing to make it plumb. Secure it to the wall with the finish nails. Measure the distance between the inside corner of this piece of casing to the other stud. It should be about 14½ inches.
Set the electric miter saw on a 45-degree angle and cut one end of the left over door casing. Measure from the inside of the casing and make a mark at the measurement from Step 1 of this section. Set the electric miter saw on the opposite 45-degree angle and cut the casing. This is the top of the door casing.
Place the top piece of casing on the wall. Be certain the miter aligns and check it with the carpenter's level. Secure it to the wall with the finish nails. Secure the final piece of door casing with the finish nails.
Secure the hinges to the 14 1/8-by-23 5/8-by-¾-inch medium density fiberboard according to the manufacturer's instructions. Place the door in the access hole and attach the hinges through the drywall to the stud. Install a knob for the door in the appropriate place and the magnetic catch to keep the door closed. Paint the door casing and door.