Sentry-bots were the robots created in the same factory that Clank came from. Clank was actually a defective Sentry-bot. Ratchet could use the Hologuise to get pass these robot guards on planet Quartu and Drek's Fleet. If Ratchet was not wearing his Hologuise, they would either shoot fire balls at him or press an alarm button to activate fort defenses for almost immediate termination. If Ratchet waved at them while using the Hologuise, they would wave back and deactivate forcefields so that he could pass.