Constructor/Reference/ObjectPropertiesForm
From TDN
[edit]
Object Properties
This menu shows you the class name, brush type and group of the object(s) you currently have selected. Using this panel you can change the brush type to structural, detail, collision, portal, trigger, vehicle collision, or other.
[edit]
Manage Entities
After pressing the "Edit Properties" button in the image above, you get this menu.