A bunker build is any build designed to hold capture points in Structured PvP. A good bunker build can easily hold 1-2 players without dying until their team comes back to assist. Bunker builds are designed for survivability, to be able to remain in the area of the capture point, and so denying the opposition starting the capture timer. Because stealth causes players to be unable to contest a capture point, thieves rarely have bunker builds. Just about every other class can fill the role, most notably the Guardian and Engineer. Both classes have a lot of control effects skills and survivability.