The SCV reappears in StarCraft II. Five SCVs can be held at a time in a command center or planetary fortress (upgraded to ten with Neosteel Frame). SCVs can patrol, a very useful ability considering they can auto-cast repair. While multiple SCVs are able to simultaneously repair a unit/structure, only one SCV can construct a structure at a time due to reasons of balance. SCVs may repair any allied unit that is considered "mechanical" regardless if it is terran or protoss, but they can only repair terran structures. It is the only terran multiplayer unit without a ranged attack.