Launch keys are a critical component aboard Colonial ships. They are used to start up a ship's power plant and engines. Their removal from a ship will immobilize it.
During a briefing aboard the battlestar Galactica, senior officers learn that grounded civilian ships on New Caprica have had their launch keys removed by Cylons occupying the planet. The keys are very hard to duplicate, and Commander Lee Adama rules out making new ones as too difficult and time consuming (TRS: "Precipice"). One of the resistance's goals is to recover them, which Lieutenant Sharon Agathon manages to do after landing covertly on the planet and infiltrating a secure storage facility (TRS: "Exodus, Part I").