Rerrin Battery is a moderately complex site which includes the following main features:
- A single 9.2-inch Mark X gun
- Two 6-inch QF guns
- A large caponier covering the north eastern approaches. This was built to hold thirty men
- An infantry redoubt protecting the high ground 150 metres southwest of the battery. See separate listing, Rerrin Infantry Redoubt.
Rerrin Battery was built between the 8th August 1898 and 31st July 1902 at a cost of £17,316. The magazines are all underground and there are concrete lined trenches linking the gun emplacements to each other.