First of all, make sure they’re completely chilled before attempting to cut them. Still-warm bars won’t cut neatly! Now grab a sharp, sturdy paring knife and score the bars where you want to cut them. You can even use a ruler to ensure they’re all the same size. Spritz some nonstick cooking spray on the knife then wipe it off with a paper towel so it doesn’t stick. Now you can line up the knife with the score marks and press it down, dragging it towards you to cut the key lime pie bars. Now they should be as neat as the ones you’d find in a bakery!