Camping stool
From Halopedia, the Halo wiki
A camping stool is a small, collapsible stool used by the UNSC to provide relatively comfortable seating in combat conditions. The stools are light and easily portable, and collapse as mentioned above so many of them can be stored in a small space.
These stools can be found on Halo 3 campaign and multiplayer levels. They are also an editable object in Forge found under the "Scenery" tab.
They are often found near Sniper Rifles and Camping spots.
