pet/child door safety question

we have a cat whose liter/food is in our basement. I am looking for a device that will keep the jar open enough that she can go up/down as she pleases, but still keep the door shut enough so that my 17 month old cant squeeze herself through the opening and fall down the stairs.

any idea of anything like that out there?

Re: pet/child door safety question

I needed something like this for a different reason.. We keep our litter boxes in the laundry room and one of my dogs just loves to go in and eat it..

So we needed to have the door open enough for the cats to go in but not the dog's head!

We ended up getting a door chain (like you'd have on your front door) and a door wedge so that the door can be "locked" into place and not open any further than the length of the chain.