Jik Uh Cha Ki, or Axe kick, can be delivered with lead or trailing leg, from offensive or defensive stance. It is performed almost identically to Ahp Cha Ohl Li Ki: Straight Leg Kick, except that once your foot reaches apogee, you will bring your heel straight down. The striking surface is the heel, and the kick is usually targetted at your opponent's face or collar bone, though it can also be effective against your opponent's thighs if they are standing in a bent-knee stance.
Please be aware that this kick is absolutely illegal in Kuk Sool Won™ point sparring. The Axe kick cannot be "pulled" - if you deliver it, you will deliver it at full force. It is therefore not suitable for use in a friendly sparring match between peers. Learn and remember this kick for use in self-defense.