The possessive form of the noun sentry is sentry's.Example: After many hours, the sentry's feet were aching.
sentry
Sentry Group was created in 1930.
Earth Sentry was created in 1999.
Sentry - Kree - was created in 1967.
Travel Sentry was created in 2003.
Sentry (GateKeeper)
Sentry - Robert Reynolds - was created in 2000.
Sentry - Curtis Elkins - was created in 1993.
Try the link to Sentry.
Contact Sentry or a qualified locksmith.
You give one of them your sentry gun find it and destroy it