I have two 6 month old kittens, and 2 labs (10 and 14 going on 15).  The
labs have a dog door that they use 24/7 to go in and outside through.  It
is one of these:
http://www.dogdoors.com/cgi/smart.cgi?command=listitems&type=group&group=best
in a large size.

Durign the night, the kittens are in the basement and the dogs are on the
porch (where the dog door is) so this is not a problem. However during the
day, all 4 animals have free rein of the house.  And I'd like to leave it
that way.

Problem is one of the Kittens have figured out how to use it to go
outside. To counter act this I've squirted him with water anytime I see
him near the door, I've bought the springs for the next size up door to
make it harder to open, and I've tried taping tin foil to the door to make
it not as inviting, to no avail.

Tomorrow I'm actually going to go and get the feline lekemia shots for
both kittens, to play it safe since currently I'm in a losing battle.
Also both cats have all claws, so that isn't a problem.  Its just that I
was planning on them being indoor cats, and would like to keep it that way.

I was wondering if anyone out there in alt.pets.cats had any suggestions
on keeping the cats away from the dog door above what I've already done.