Things You'll Need
Metal corner bead
Drywall nails or screws
Hammer or screw gun
90-minute quick-setting joint compound
Bucket of room-temperature water
6- and 12-inch drywall knives
100- and 150-grit sandpaper
Drywall is fragile, so the best way to protect the outside edges around a doorway is to install metal corner beads, which are long strips of metal that have a 90-degree bend along their length. Metal corner bead creates strong, straight corners that can withstand the occasional blows that occur in a high-traffic area. The quickest way to finish the metal corner beads after you hang them is to use 90-minute quick-setting joint compound, which is available at most retail building-supply stores. It will dry quickly, but still give you enough time to work with it.
Cut metal corner bead to match each outside edge on the doorway. Typically, this amounts to six pieces total — four pieces for the vertical edges (two on each side of the doorway), and two for the horizontal edges (the top of the doorway). Use construction scissors to cut the corner bead. Be careful not to bend the corner bead, or it will not lay straight on the corner.
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Place a piece of corner bead on an outside edge of the doorway. Hold it gently in place with one hand while you install a drywall nail or screw through one of the small holes on the edges of the corner bead. Don't install the nail or screw too deep, or you will warp the corner bead. Continue installing nails or screws every 4 to 5 inches on both leaves of the corner bead. Repeat the process for each piece of corner bead.
Make a mixture of quick-setting joint compound and water. Follow the manufacturer's instructions exactly. Typically, you will have to add powdered joint compound to a bucket of room-temperature water while mixing vigorously. Do not reverse the order and add water to the powder, or the final mixture will be lumpy and difficult to use.
Apply the quick-setting joint compound to the corner bead. To do this, put a large amount of joint compound on a 6-inch drywall knife. Wipe the joint compound onto the corner bead with a smooth motion, filling the valley formed by each corner bead. When you finish, the only visible part of the corner bead should be the metal edge. Repeat for each corner bead. Allow your work to dry for 90 minutes.
Make a second batch of quick-setting joint compound and repeat the coating process, this time using a 12-inch drywall knife to cover the corner beads. Allow everything to dry for 90 minutes.
Sand the doorway with 100-grit sandpaper until it is completely smooth.
Make a third batch of quick-setting joint compound, but this time make it thinner by adding a few cups more water than you did for the first two batches. Aim for a consistency a bit thinner than toothpaste. Use a 12-inch drywall knife to apply a thin coat of the new mixture over the corner bead. Allow it to dry for 90 minutes.
Finish the doorway by sanding it gently with 150-grit sandpaper.