Taking the place of your normal quick-release skewers, OnGuard's Locking Skewer Set keeps your wheels from being an easy target. The system is keyless and tool-less for easy installation. They use an innovative patented lock system to prevent the QR from opening unless the bike is tilted over 90 degrees from level. Simply lock your bike with wheels attached so that it can't be tipped more than 90 degrees. To unlock, tip your bike past 90 degrees and open the QR levers.