Because cannabinoids are not combusted, fewer burn and thus more can be inhaled and put to use within the body. Hence, knife hits are more potent and less is necessary to feel its effects. Knife hits are a healthier, more efficient way to consume and conserve cannabis flower.
Heat up a butter knife, preferably with a blowtorch—a stove top, Bunsen burner or campfire will also suffice. When you're ready to take your hit, stick the hot knife through the slot you've made. Touch the oil to the hot knife, and inhale through the top of the bottle.