Shield

Were you referring to:
 * Energy Shields, a technology utilised by both Covenant and UNSC supersoldiers which provides limited protection?
 * Shield Generator (Covenant), the Covenant structure which provides limited protection in Halo Wars?
 * Stationary Shield Generator, the device used by the Covenant during offensive ground operations?
 * MJOLNIR Shield Tester, a machine which generates the MJOLNIR's shield system?
 * Bubble Shield, a Covenant personal defence device?
 * Shield Door, a Forerunner energy shield which only repels gunfire?