Beg your pardon but a slim most certainly is ,as also screw drivers and lawn mower blades.
I have experience using one to open car doors, and as far as I know that's what they're designed for. I've never seen a house door or window that has a lock or latch mechanism that would require that kind of tool. I can see that you could possibly use one on a spring-loaded, or flip latch, but a simple credit card or pocket knife would work much better, and having those in your posession doesn't arouse suspicion. It makes no sense to me.