1. Prevents ashes from getting sucked into your mouth.
2. Prevents ashes from burning into the bowl and damaging the pipe.
3. Prevent the ashes from clogging the air holes at the bottom of the pipe, so that the airflow can be smoother to help the burning.
Step 1: Put the screens into the bowl opening.
Step 2: Press down firmly with a stick or some pipe tool.
Step 3: Make sure the screen is secured in place.