For drilling in wood, metal or other material coming out. It should lay flat materials up the bottom hole drilling, drill, drilling through out. To prevent debris from wooden fins are simply no rupture or tear protection.
For drilling materials to penetrate the wood or metal. Leftovers should be laid flat pad below the stave to drill through it. To prevent debris from penetrating rays or prevent rupture uneven.
For the drilling material through the wood, or metal. The scrap material to the smooth below stave to drill through out. In order to prevent debris from penetrating the fin or prevent wood tear break even.