Launch key
From Battlestar Wiki, the free, open content Battlestar Galactica encyclopedia and episode guide
Launch keys are a critical component aboard Colonial ships. They are used, apparently, to start up a ship's powerplant and engines, similar to the way a car key does for the average automobile. Their removal from a ship will immobilize it.
In "Precipice", a briefing aboard Galactica reveals that the grounded ships of the Fleet have had their launch keys removed.