To cut Sheetrock, also known as drywall, mark the cut, score the drywall, snap the drywall, and then make smaller cuts as needed. You need a t-square, chalk and a utility knife.
- Mark the cut
Place a t-square along the top of the Sheetrock where you wish to make the cut. The top of the t-square rests on the edge of the drywall at a 90-degree angle to the part of the square marking the cutting line. Mark the drywall with a piece of chalk along the cutting line to provide a visible line in case the t-square shifts.
- Score the drywall
Use a utility knife to score the drywall by drawing it across the surface of the sheet along the cutting line. Hold the t-square in place to drive the blade along to keep the line straight. The scored cut does not have to be deep, only deep enough to barely cut through the paper. If the piece being cut from the drywall has a width less than 3 inches, then score the rear of the sheet along the same line.
- Snap the drywall
Set the Sheetrock flat onto the floor, scored side down. Pull the Sheetrock upwards towards the scored line. The drywall will snap along the line, leaving the unscored front paper piece intact. Draw the utility knife along the attached piece of paper to complete the cut. If the sheet is scored on both sides, then the small piece will come away instantly.
- Make smaller cuts
Make smaller cuts in the Sheetrock, for windows for example, by using a drywall saw to cut from the edges, or a drywall keyhole saw to cut from the center of the sheet. Make centered cuts while the sheet is still unattached to the framework of the room. The longer edged cuts are made after attaching the sheets by making vertical cuts upwards using the drywall saw, and then making horizontal cuts by scoring the rear of the drywall with the utility knife and then snapping the board forward before cutting the front piece.