The 17-year-old boys went to the Junior Reserves and the 45-50 -year-old men went to the Senior Reserves. Those not joining these reserves were drafted into regular combat units. When a member of the Junior Reserves turned 18, he was expected to transfer to a combat unit.
The Junior and Senior Reserves guarded key military sites like bridges, railway depots and prisons in the states from which they were organized (apparently, other Confederate attacks had Junior and Senior reserves). This released soldiers who were previously assigned these duties to combat duties.
The Reserves were not supposed to leave their home state, but that was suspended in the dire days as the war waned in late 1864. The North Carolina Junior reserves briefly went to Virginia on two occasions.