The pale yellow faces and their bounding edges are hidden when the exterior is shown.
(Image from my castle)
When you have a big model with groups as different section (usually floors) you may want to hide the faces where the groups touches when you look at the exterior, but show them when certain groups (such as the upper floors) are hidden. This tutorial tells a bit more about dividing models this way.
Hide Cut Surfaces
This tool loops through all faces in groups in the model root, and move them among with their bounding edges to a special layer if the material is considered a cut material. For this to work the material must be named "!Cut!" or "!Cut#n!" where n is any integer.
The user will have to create different scenes for different groups (floors) and one exterior view. These scenes are used to show and hide different groups and the exterior scene also hides the section cuts. Don't save camera location to these scenes if you want to be able to change floor without moving the camera.
Installation: Unzip all files and folders to the plugin folder