A belated thank you for all the excellent suggestions I received to my frantic question. (And my apologies for not responding sooner!, with a snow storm delaying my collecting my new furry family members and last minute essential condo revisions things went a little nuts around when I posted my question!)
A little confession here, no idea what a binder clip is, and must admit the two people I asked didn’t know either. (Which made me feel a little less dim.)
I thought of a clothes pin but was scared it wouldn’t close tightly enough (I may not have the right kind) and that it could be pushed off. Had a dog years ago who could do that with his crate door (that and a lot else, he was very bright and small so I don’t judge by size) made me uneasy about trying that. Why a small lock didn’t occur to me I’ll never know why not, terrific idea and wish I’d seen it sooner. Beka, your message about the leash clips did send me back to check again and at least clued me in as to what the problem was, short version is the ones I had were way too small. I got a larger variation in the end (in a mad rush actually) and they are working well.
I’ve come to the conclusion that an NIC condo is one of those awful things you only really know how you should have built once you’ve made one. However, its working quite well, and fortunately I haven’t installed two critics, so far as I can tell I’m pretty much getting rave reviews now that I made a couple of adjustments based on observing them in it.
Thanks again to all of you for all your great ideas, I will be remembering them for future reference!