The four possibilities are: (they are not always all offered on
any specific door model or by a specific manufacturer).
On arch-top door sets, this choice is NEVER available! Any vibration would let the two screens to slide down hill and to open unintentionally. In addition, the taller screen necessary near the middle would hit the floor when it got near the side!
JDoor's
Fireplace Door Selector Page is at:
http://mb-soft.com/juca/info/doors/firedoor.html