Repairs nearby stationary vehicles, buildings, and emplacements that are out of combat.
The Repair Bunker is a Wehrmacht structure. In skirmishes, it cannot be built directly and instead is a conversion upgrade to the Concrete Bunker.
Once a Concrete Bunker is converted into the Repair Bunker, it loses its ability to garrison troops. Instead, it will passively heal nearby damaged friendly vehicles and structures. This includes teammate units/structures, as well as the bunker itself.
The bunker repairs at a rate of +6 health per second, which is a bit slower than the standard rate of +8 that most engineer units can repair at.
As with any other structure, it is quite hardy against small arms but is vulnerable to artillery, anti-tank weapons, and flamethrowers.