Weapons lockers are storage facilities for weapons aboard a battlestar. Typically, these include small-arms lockers, but larger weapons and artillery are likely kept in these sections as well.
Standard procedure in the Colonial Fleet for weapons lockers is to place them under marine guard, with logs on who has entered and exited these lockers. However, in the weeks following the Fall of the Twelve Colonies, Galactica's facilities were unguarded, allowing Sharon "Boomer" Valerii to take G-4 and their detonators and to use them in destroying Galactica's water tanks (Water). However, despite rectifying this oversight, a marine guard is killed by a Number Five infiltrator who takes explosives for a suicide bombing (Litmus).
Aside from first appearing in "Water", and a mention in "Litmus", a small-arms locker is seen again in "Valley of Darkness", where Lee Adama, Louanne Katraine and a few marines encounter James "Jammer" Lyman.
A second notable appearance occurs later in "The Ties That Bind" in the form of "Weapons Locker 1701D", where Tory Foster, Saul Tigh and Galen Tyrol meet. Cally Tyrol follows them to this locker, entering a crawlspace adjoining the room, and learns of their nature as Cylons.