I cant find the camera, so I've drawn a picture instead.
The red part is the one I want to remove. I think the main bracings would be the ones running from top to bottom, where else the one I want to remove would be a side bracing maybe? Underneath the bracings are another piece of glass, so that the covers can be put on it.
If thats still not clear, I'll go borrow a camera. My tank dimensions are 900x450x450.
Edit - Picture had problems, and the drawing is not to scale.