The Praefectus Castrorum (lat. commander of camp) was a third-highest officer of the Legion and led the Legion, if Legatus and Tribunus Laticlavius should be absent. He was in principle an administrative boss of the Legion and ensured for the fact that all regularly taking place actions run off smoothly. Barracks, guards, military hospital, workshops and the cannon park in the camp stood under its upper supervision. As such it is to the Legatus also as a planner at the disposal.
Usually the Praefectus Castrorum from the career of the Centurionen had ascended, i.e. also not-noble of military could occupy this post.