Things You'll Need
Plywood cutting blade
Plastic cutting boards come in a wide variety of sizes. Because of this you might find that your current cutting board is too long for your needs. There is no sense in purchasing a shorter cutting board when you can cut down your existing one. When you cut a plastic cutting board, you should always wear eye protection to protect your eyes from flying bits of plastic. There are several ways to cut a plastic cutting board, however the simplest way is to simply cut it as you would a piece of wood.
Place the end of the tape measure on one corner of the end you want to cut off the plastic cutting board. Measure down the number of inches you wish to cut off and make a mark on the cutting board with washable marker.
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Move the tape measure to the other corner and make a mark at the same measurement. Place a ruler or other straight edge across the two marks and draw a light line onto the cutting board with the marker.
Install a carbide-tipped plywood cutting blade into your circular saw. The plywood blade uses smaller teeth that are closer together than a regular blade and cuts through the plastic cleaner than a standard blade.
Clamp the plastic cutting board to a workbench with the cut line hanging over the edge of the bench. Line up the saw blade with the cut line and cut the plastic cutting board. If you do not have a circular saw, cut the plastic cutting board with a hacksaw.
Wash the plastic cutting board thoroughly once you finish making the cut.
If necessary, clamp a piece of straight wood to the cutting board to serve as a cut fence for the circular saw. Also, make the cutting marks on the back of the cutting board.