Tilley Radiator Guard

Could someone please advise the purpose of the flappy bit on a Tilley radiator guard. Thank you in anticipation of informative replies.

Ray

 

So that the draught shield can be fitted without removing the guard.

 

Thus it goes at the top and not, as often seen, at the bottom where, presumably, someone thinks it is to allow access to the control cock. It also falls open when placed at the bottom so that's obviously not right...

 

Not a brilliant video, but at least it shows the draught shield.

https://www.youtube.com/watch?v=o3btF4ldlJc

 

Thank you again for the info, now need to find a burner and we're off.