Yeojang (女墻 or 女牆) and Chi (雉)
The yeojang is a parapet looks like a low, shallow wall built on top of the main wall to protect defenders from enemy arrows or bullets. The chi is a reinforced work, looks like a protrusion on the outer side of the main wall that enables defenders to shoot at attackers from various angles.
Poru (砲壘 bastion with cannon embrasures)
This is a parapet with embrasures on the top of bastion for firing cannons. The Korean military suffered bitter experiences in the Imjin War with Japan (1592-98) and the Manchu Invasions of 1627 and 1636. As a result, military tactics were changed, and the Korean army began to use cannon and matchlock rifles. This required that new facilities be built at the fortresses, and the walls had to be reinforced to withstand attacks from cannon and firearms.
Jangdae (將臺 command post)
"Jangdae" refers to the a 2-story pavilion used as a lookout for commanders to direct the battle. Originally, Namhan Mountain Fortress had five (including ones in each of the four directions), but today only Sueojangdae (守禦將臺) remains.