Weird one this, but thought I saw a picture one time of a guy with lens and collar and there was metal tie or chain from the collar back under the dslr screw mount underneath , so that in case the lens came off the mount, it would still be left dangling from under the camera. I went on to adorama and searched lens chain and lens wire etc, but can't find it, maybe there's a different term. If anyone knows what I'm talking about and can post link, I'd appreciate it, thanks.