Child proof catches

I bought some fab ones years ago for my rat aivary I had in my classroom which were eay to open once you knew how, but the children couldn't work it out!
They were like little silver clips that you pulled out a square pin to release to loop to open.
They were really quick and easy. I've since used the ones I had on my coop as the children (and therefor foxes) can open them easily.

I'm after some more, or equivilent little locks. Doesn't anyone know of anything??
I cant find them anymore online and can't remember where I bought them!! Grrr frustrating!!

I think I know what you mean as I have used them. They sell them at our local plumbing/building etc shop. Ours is called Hursts it's like an ironmongers.

Just what I was looking for too