A laminate countertop should be accompanied by a laminate backsplash. The backsplash can range in height -- from a several inches to a few feet. Normally, the backsplash is cut before it is installed. Before installation, you can set the laminate piece on two sawhorses for cutting. If the laminate is already installed, you can still cut it down but the wall texture underneath the laminate will probably need to be refinished afterwards.
Mark the area that you want to cut on the laminate backsplash with a pen. Extend a measuring tape to create a straight cut line.
Place a piece of masking tape over the marked line where you will cut. Line an additional piece of masking tape on top of it. The tape will mark your measurement and prevent the laminate from being scratched or chipped during cutting.
Draw another cut line with your pen over the masking tape since the tape is now covering the original mark. Remeasure the backsplash if necessary.
Measure the depth of the backsplash.
Set the depth of the circular saw to 1/8 of an inch deeper than the thickest part of the countertop.
Turn on the circular saw and allow the blade to get to full speed.
Place the saw flat on the surface, so the blade is lined up with the mark. Cut the backsplash along the measurement mark using the saw.
Sand the cut edge of the backsplash using 220-grit sandpaper after the cut is complete. Make sure to sand downwards, so you don't accidentally pull up the laminate.