Query re inward opening upvc double doors

[ZeitGeist]

Hi,

I had a 4ft wide set of inward opening upvc doors installed. Hinges are about 6 inches from both the top and botom of each door. Halfway between each set of hinges is a small stubb coming off each door - I could see no purpose for these. However, should these fit into a receiver behind the frame to force the centre part of each doorframe against the rubber sealing strip that is on the roomside of the frame? (Because their isn't one and I begin to think there should be, so that the middle of the door can't flex away from the frame when closed)

TIA

[Invisible Man]

Could they be hinge/dog bolts? For outward opening doors they maintain security in case a thief knocks out the hinge pins. Not necessary on inward opening doors where the hinges are inaccessible. Would expect to see more than 1 a door though. Perhaps they are deigned to locate the centre of the door though or strengthen it. I would have expected 3 hinges per door.

[ZeitGeist]

Thanks.