Well as any child will tell you, is when it's a jar, get it?
Well this door has never been open far less ajar. Most people think it's a Georgian Tax saving scheme to avoid window tax! of which there are many examples across Glasgow and the rest of the UK (Window tax applied to anyone with more than six windows). In fact I've seen boarded up windows as far afield as Florence in Italy.
No these fake windows and door are just architectural devices to give the building symetry. The roof and gable end support a chimney. The fireplaces were on each floor and flues running behind the wall. Close examination of the door reveals no handle, hinge or lock. It's all fake, it's never been a door.
Where? Virginia St, Glasgow. Part of my Glasgow's dark and mysterious past.