Cut plastic by marking the area to be cut with a pencil and making several passes over the mark with a sharp utility knife. Turn the plastic over, and snap the edges together so that it folds. If necessary, trim along the fold with the knife, and sand rough edges.
- Mark the cut
Measure carefully, and mark the cut using a straight edge and a sharp pencil. For curves, use a French curve or compass to keep the line smooth.
- Score the plastic with a utility knife
Hold the straight edge along the cut mark. Run a sharp utility knife along the straight edge to score the cut. Repeat three or four times, going a little deeper with each pass. Score curves with the help of a French curve.
- Snap the plastic
Turn the plastic over. Hold the edges on either side of the cut mark, and snap them together to fold or break the plastic along the scored line.
- Finish the cut with a utility knife
If the plastic did not break all the way through, run a utility knife along the fold to finish the cut.
- Sand the cut edges
Rub a sanding block along both cut edges to remove roughness.