Drywall boards have two types of edges to them: the butt end and the tapered end. Unlike the tapered ends, butt ends make poor seams because the joint compound and tape used to conceal the joint often bulge out and ruin the appearance of a perfectly flat wall. Butt ends are best installed in corners or by openings such as around windows and doors, but you can easily taper the edge to make a suitable joint. Even with the tapered butt joint edge, the seam may bulge slightly after applying joint compound. When applying the compound, take your time creating a very smooth, wide seam to avoid unsightly bulges.
Screw the board onto its place on the wall or ceiling. If the stud or joist is narrow or the butt joint is situated over a doorway or window, screw a large scrap piece of wood onto the side of the stud or joist. The extra wood gives you more backing with which to secure screws to the drywall board, preventing the seam from pulling out later.
Cut the butt end of the drywall board at a shallow 45-degree angle with the utility knife. This will create a tapered trough along the butt end, enabling you to fill the void with joint compound.
Remove any paper shavings from the tapered edge of the board with your fingers or with a rasp. This will prevent the paper pieces from popping up through the joint compound when you apply it to the butt joint seams.
Lay a thick coat of joint compound into the tapered butt seam with your 4-inch compound knife. Press the compound into the tapered edge, to fill the void completely. Apply one long strip of mesh or paper tape from one end of the tapered butt seam to the other.
Lay a thin coat of joint compound to the seam with your 6-inch compound knife to cover the mesh or paper tape. Allow the compound to dry completely.
Gently sand the seam smooth. Avoid sanding through to the mesh or paper tape, as the tape will fray and ruin the seam.
Apply a thin coat of joint compound to the seam with your 6-inch compound knife. Allow to dry completely and sand again.
Apply a final coat of joint compound with an 10-inch compound knife. For a perfectly smooth seam, fill the knife with several scoops of joint compound: Begin at one end of the seam and slowly smooth the compound down the seam as evenly as possible without stopping the motion.
Allow the compound to dry completely. Sand the seam smooth.
If you have two butt ends meeting at one seam, cut both boards in the 45-degree angle to create a "V" groove between the boards. The "V" groove will hold the joint compound and provide a secure seam. To further reduce a bulge at the seam, you can apply the joint compound layers without the tape. Realise that the seam may crack if the compound dries too quickly or if the wall or ceiling settles, however.
Do not screw too close to the edge of the tapered end or the screws will break the drywall off the edge. If your taper is very wide or the studs and joints are very narrow, be sure to screw a piece of scrap wood to serve as extra backing support for the drywall screws.