Catwalk (Portal 2)
The Catwalk in Portal 2, used in behind the scenes sections in the game, is a series of models found in the game under the prefix hanging_walkway_... and found in the folder catwalk_destruction.They can be placed in the game as a prop using these as world models. There are also animated versions of catwalks, which are catwalks being demolished.
List of models
Still models (under the folder catwalk_destruction)
Animated models (under the folder catwalk_destruction)