Hardened plates protect your skin and help you deflect physical blows. A limb with dermal plating functions as a shield. You can
Raise a Shield with your limb, giving you a +1 circumstance bonus to AC until the start of your next turn, but it doesn't require a hand to use. You can use the
Shield Block reaction with your limb. Dermal plating has Hardness 5. After you use Shield Block, your dermal plating becomes damaged and can't be used for 24 hours as the nanites repair the durable plates.