Cutting a sheet cake often can be a frustrating, messy process because no matter how hard you try, the cake crumbles or sticks to the knife. Next time, try cutting the cake this no-muss, no-fuss way with a piece of unwaxed dental floss. The size of the pieces will depend on the number of people you are serving, but between two and three inches is the standard serving size.
Set the sheet cake on a solid surface so that it will not slide easily. If it does, put it on a damp kitchen towel.
Wrap a long piece of unwaxed dental floss around each of your index fingers. The dental floss should be 12 to 15 inches longer than the height of the cake.
Cut the cake starting two inches in from a narrow end of the cake. Cut by sawing back and forth with the dental floss. Let go of one end of the dental floss, and slide it carefully out of the cake.
Move in two to three inches from the first cut, and re-wrap the dental floss around your index fingers. Make another cut, and repeat until you get to the opposite end of the cake.
Turn the cake and cut it horizontally, using the same technique. Continue until you reach the end of the cake.
To make the sheet cake even easier to cut, put it in the freezer for a few hours. The cake will be firmer and will hold together. If you want the pieces of cake to be perfectly sized, measure the pieces before you cut the cake, and make a tiny mark with a toothpick for each cut. A full sheet cake (12 x 18) should yield 45, two- by three-inch slices.