Wolfenstein: Enemy Territory Documentation
© 2003 Splash Damage, Ltd. All Rights Reserved.

Appendix C: Common Textures
common/caulk A structural and invisible shader. Used to create the structural 'hull' of the BSP. common/clip Standard Clip brush which will block players.
No bullets or projectiles are blocked.
common/hint Forces additional portals in the BSP. common/clipmissile Based on the standard clip brush. Blocks all projectiles.
common/ladder Allows players to climb up or down. Acts like player clip. It must be present on all sides of the brush. common/clipweapmetal Based on standard clip brush. Blocks all projectiles and produces a metal sound when hit by bullets.
common/lightgrid Defines a volume where the lightgrid is active. Any space outside is not calculated. common/clipweapwood Based on standard clip brush. Blocks all projectiles and produces a wood sound when hit by bullets.
common/nodraw Does not draw in game and is non solid. Used for single sided brushwork like alpha channel textures. common/terrain Terrain metashader with grass step sound.
common/origin Used by brushwork entities for defining their origin point in the map. common/terrain_sand Terrain metashader with gravel step sound.
common/skip Skip is a nonsolid, invisible, structural shader that does not create BSP splits or portals. Used in conjunction with antiportals or hint faces. common/terrain_snow Terrain metashader with snow step sound.
common/trigger Used on brushwork trigger entities. It's not drawn and is not solid.    

Please note that this is not a complete list of texture/shaders from the common directory but a summary of the most useful ones for producing a map for Enemy Territory.