Micro-maneuvering controls were controls that allowed starfighters to perform fine maneuvers in tight spaces. In T-65B X-wings, they would fail if the fighter's stern hydraulic lines were compromised.
Wedge Antilles flew in the Battle of Yavin in an X-wing with haphazardly-patched hydraulic lines, and was forced to pull out of his trench run after they were severed by TIE fighter fire and losing his micro-maneuvering controls.