Snapshot 14w28b Visual Iron Trapdoor Bug

I found a new visual bug with the new Iron Trapdoors. I'm currently checking in with snapshot it started occurring, but I just wanted to show it before someone els does. I made a video about it in which I explain it. I think this bug would be great for hidden rooms en stuff like that. Please check out the video and tell me what you would do with it. Also tell me if someone els found this already.
My video: https://www.youtube.com/watch?v=bIsR1zqM4YU