Seagull Stopper Dock Defender 8 Post System is a bird deterrent/repellent that is designed to KEEP SEAGULLS and WATERFOWL OFF YOUR DOCK SYSTEM - 8 Magnet-and-Staff Assemblies suspend heavy test monofilament line along the side of your dock. Based upon the successful hoist canopy protection product by Seagull Stopper, birds avoid areas that are protected by fishing line as they are unable to take off and land safely. After initial placement of the striker plate, this product attaches magnetically making installation and removal a snap.