Mark the cut line with a ruler and pencil
Place the foam board on a cutting mat or scrap surface
Use a sharp utility knife, craft knife, or foam board cutter
Hold a metal straightedge firmly along the marked line
Score the foam board lightly on the first pass
Make several additional passes until the cut goes through
Keep the blade angled slightly for a cleaner edge
Replace dull blades often
Cut slowly and steadily
Use a fresh blade for thick foam board
Cut in one direction to reduce tearing
Trim any rough edges with the knife
Wear cut-resistant gloves if needed
Use a dust mask if cutting produces particles
Keep fingers away from the blade path