These ‘bleeder’ screws are to designed to allow the rider to remove any excess air pressure that gets trapped in the fork uppers during use. This can happen during hard compressions, large temperature swings, or large changes in elevation such as when traveling to new regions. By removing any trapped air, you will maintain the smoothest possible operation of the fork and maintain your ability to use full travel. For best performance, remove and reinstall the bleed screws often. Once every several weeks is sufficient for most riders.