Hi, I have the same problem, my eldest cat " MILLIE " learnt to do this months ago, we have new additions to our family and we have to be really on guard because 1 of the little ones managed to follow her while she was on her way out, sneaky eh! After what happen to my dearest "MERLIN" back in May against everything I believed in of letting cats having their freedom I'm bringing the 2 new kittens up as house cats, I just couldn't go through that heart ache again. X X X :-)