Sentries are objectives in World versus World. They are posted with a single Veteran Guard, and can typically be found along supply routes. They will cripple and attempt to kill any enemy dolyaks that attempt to walk past, and will mark any enemy players that stray too close, enabling your team to spot them as red dots on the map. Killing the guard allows you to capture the objective for your world.
A First Aid Kit can also be found at sentry posts.