How to click ! Step 1. Put the metal-chip on your fingers. Step 2. Put your big finger on the middle of the chip. Step 3. Push it with your big finger until you can hear a sound "Tip-Tok". Step 4. Take out your big finger. For HOT ; Snap the metal-chip inside the pack slightly. This will initiate a chemical reaction that causes the pack to heat up and harden. Hot Pack will stay warm for several hours.     Wrap the used-pack in a cloth or towel. Immerse in boiling water for approximately 10 to 20 minutes, until all crystals within the pack have disappeared. Do not place it directly on skin after boiling and do not puncture. Do not bend the metal-chip inside the pack.