From Valve Developer Community
Tip:Only use this entity if you are desperate. It is much better to assign a material a %detailtype and let VBSP generate detail sprites itself.
Note:This is an internal entity. When the map is compiled by VBSP it is processed and then removed: it does not exist when the map is running.
This entity is not in Valve's FGDs. Its properties must be set with SmartEdit disabled.
- Standard position information.
- See Detail props#sprites.
- Confirm:The location of the sprite's upper left and lower right corners, relative to its origin.
- The area of the detail texture that should constitute this sprite. See Detail props#sprites.