"I used to be a Carpenter, you know!" - Nikolai Belinski on the Classic Maps.
Carpenter is a power-up that was introduced in Der Riese. If it is taken, all windows will be repaired and the players will get 200 points if there is at least one fully boarded window before the power-up was taken. This is 400 points when Double Points is active (Not in World at War).
Knowing what this power-up can do, it is advisable to take it whenever it appears. Even though some players do not count this power-up as helpful, it actually does save some time from zombies coming through barriers with boards. This is great for if you have recently gone down and need to get your perks back because it can keep the zombies at bay while you drink up your magical sodas. The moment of peace provided by the Carpenter is also a nice break sometimes.