CQ or Charge of Quarters is a United States armed forces term used to describe tasked duty in which a service member is to guard the front entrance to the barracks. It is usually a 24 hour shift in which the two service members, one non-commissioned officer (NCO) and the other a lower enlisted service member, sit at a desk and monitor incoming and outgoing traffic into the barracks. There are usually some duties like sweeping and mopping the entryway, cleaning the entrance restrooms and performing radio checks every few hours with other company barracks and battalion headquarters around the base or surrounding installations.
Other duties may include checking the barracks laundry room for laundry left over night, bed checks to ensure service members are in their rooms with their doors locked by curfew, for example, all U.S. Armed Forces service members stationed in South Korea have a curfew for being on post, and another one for being in their own individual rooms with their doors locked.
Shifts usually start just before work call in the morning depending on the branch and installation and go for 24 hours. Service members are typically excused from duties the following day after this shift to allow for rest.