[Tee]

There's a transparent object just like glass but it's not glass, does anyone know the ID?

[EAsT-OAK_510]

Please be more specific.

[Threshold]

If you could provide a picture or something, that would be helpful. Also, if you're looking for an invisible barrier, I know that you can flip the runway found on the ship in one of Toreno's mission (Single Player), and the underside is invisible and can act as an invisible wall.