Sentry bot Sentry bot is a robot that appears in " Fallout 2 " , " Fallout 3 " , " " , and " Fallout 4 " . Background . < section begin = " Background " / > Sentry bots ( military serial numbers SB - XXXX ) are security robots made before the Great War with the express purpose of participating in the heaviest of firefights during war . Where the Mister Gutsy is a hovering platform with modest armor plating , and the protectron was originally designed for protecting business premises , the sentry bot is a powerhouse , equipped with sturdy armor plating , powerful weapons integrated into its chassis and high mobility , thanks to mecanum wheels mounted on its three legs . < section end = " Background " / > Variants . Sentry bot . Sentry bots are one of the highest level robot characters , and are much more powerful opponents than protectron s , robobrain s and Mister Gutsy models . Their purpose is mainly to guard locations for high profile characters and organizations , such as REPCONN in " " . In " Fallout 3 " they will be more encountered in office buildings and pose a serious threat , wielding missile launcher s and Gatling laser s . Three standard variants exist . The " Fallout 2 " variant is shaped like a bipedal mech , standing about the height of a super mutant and is capable of walking . The Fallout 4 variant is much bulkier , can accommodate dual mortars , and has a cooldown mode that is activated if the robot fights for too long . Enclave sentry bot . Slightly darker in appearance when compared to the normal variant , the Enclave model boasts improved systems . They appear at Raven Rock and alongside Enclave squads in the wasteland . During Broken Steel they are encountered guarding Adams Air Force Base . U . S . Army sentry bot . Military robots from before the Great War , painted in the characteristic olive green of the U . S . Army . They can be encountered at Fort Constantine , the National Guard depot and when wandering around the wasteland . Strike team sentry bot . The most expensive option for recruitment in " " is a winterized sentry bot , with a built - in minigun and missile launcher , costing 4 recruitment markers . Presidential metro sentinal unit . This unique sentry bot is encountered in Broken Steel , at the end of the Presidential metro , near the metro to Adams Air Force Base . It holds the main fuse , which is needed to repair the nearby powerbox for the metro . Hardened sentry bot . A hardened sentry bot is a hardened version of the military sentry bot . They are Enclave affiliated , encountered along with around the crashed vertibird in the Mojave Wasteland . Prototype sentry bot . An antique prototype version that can be found in the museum inside REPCONN headquarters . It has four wheels instead of the standard three , a set of arms stemming from its back and arching around over its shoulders . Where the arms would normally join the main body in current models , it includes 3 jets on each side , as used by Mister Gutsy / Handy robots . Mark series . The sentry bot mark series appears only in the " " " Old World Blues " . NCR sentry bot . It is similar to the military sentry bot in appearance , but is differently colored , with orange eyes instead of the standard red . The NCR sentry bot was originally intended to be stationed in Camp McCarran , evident in its G . E . C . K . id McCarranFieldSentryBot , but was cut from the final version of " " . Siege breaker sentry bot . A siege breaker sentry bot is a slightly upgraded version of the normal sentry bot , only appearing in " Fallout 4 " . They can be dangerous opponents for lower level players .