A fuller is a groove or channel applied to a knife blade to decrease weight and increase strength. Fullers may be ground from or pressed into the blade, however only pressing increases rigidity. This is because it increases the folds in the metal billit, much like the pressed receiver on the M3A1 or an origami bottle-opener. Grinding a fuller into a knife will only decrease the weight, but at a significantly lower cost compared to fully ventilating the blade.