If you need know how to cut foam, the following instructions should give you all the information you need.
Step 1 - Measuring the Foam
There are many reasons to cut foam, and many potential shapes you will want to be able to cut it into. Whatever your finished project will be, it is important to plan ahead correctly. Figure out the dimensions of the piece of foam that you need, and then measure your foam with a ruler. Make marks using your marker wherever you need to make a cut.
Step 2 - Preparing to Cut
Place your ruler along one of the lines you have made on your foam. Get out your utility knife and hold it over the foam and touching the ruler, using it as a guide.
Step 3 - Cutting the Foam
Press your utility knife down firmly. You should be able to make a neat slice directly through the foam. Continue to use the ruler as a guide to keep your cut nice and even.
If you are cutting foam board or a stiff material, you may opt to score along the line you have drawn and then snap the board in half neatly. Additionally, for larger pieces of foam you may need an electric knife or even a bandsaw.