cat flaps when in a tunnel configuration

[Zenith (Liz)]

My mum and dad only have one flap

[Gill (sneakiefeline)]

My brothers has a flap each end too 

[Gillian Harvey]

But if you have a cat flap which has a tunnel (ie through a wall) - do you actually have a flap each end or is it purely on the inside that the flap is?

Ah, I just answered on your other thread! - but anyway, when my mum had a tunnel in the wall for the cats, there was a flap each end.

[scattycat]

This is going to sound really thick ...

But if you have a cat flap which has a tunnel (ie through a wall) - do you actually have a flap each end or is it purely on the inside that the flap is?

I dont seem to be able to find any pictures on the net showing this type of thing - am just wondering what happens if theres only the flap on the inside - do you then just have a large hole/tunnell that they walk through and then get inside?