Using the Plumb - Rite® 400GP Plumb Bob is easy. First, choose the right attachment method according to the surface. If it's wood or drywall, use the setting pin. For steel surfaces, rely on the strong magnet. You can also hook it onto nails or studs. When using, let the self - retracting line out and wait for the 14 oz/400 g bob to stabilize quickly for accurate alignment. As for maintenance, keep the elastomer - wrapped heavy - duty case clean. Check the reinforced setting pin head regularly for any signs of wear. Be careful not to drop the bob from a great height to avoid damage to the internal components.