A coving is a moulding that accentuates borders on a ceiling or wall. It's shaped in an arched quarter circle, giving a softer look to the borders of walls and ceilings. Cutting corners in coving can be done externally and internally. External corners are the wall edges that jut out; internal corner describes where two walls meet inward. All coving cuts are made in 45-degree angles, and require the use of a mitre box for exact cuts.
Place the coving in a mitre box. Make sure that the back of the coving is flush against the box.
Cut at a 90-degree angle for straight cuts. Use the centre slots to make the straight cut.
Position the saw at a 45-degree angle with the saw pointing to the right. Use the lower left slot with the upper right slot to make the cut. Use the right side of the cut piece for internal right corners. Use the left side for external left corners.
Cut the cornice at a 45-degree angle with the saw pointing toward the left side. Use the lower right slot with the upper left slot to make the cut. Use the right side of the cut piece for the external right corners. Use the left side for internal left corners.
Since coving is flexible, don't apply too much pressure while cutting, or it might break.