Fort Ruger was located in and around Diamond Head. The interior of the volcanic cone was accessible through two tunnels large enough for trucks. The administrative buildings were on the north side of the cone. The batteries included mortars placed when the fort was built, dating to 1910. Battery Ruger, like all of the 155mm batteries, were temporary emplacements using four Panama mounts, a circular track surrounding a center pivot where a 155mm GPF gun was mounted. Battery Granger Adams was a typical pre-World War II coast defense emplacement, with the magazine in a protected bunker and the guns behind parapets in open mounts. It was built 1933-1935, with two 8-inch guns.