When I was first experimenting with bones I stumbled on a configuration that made the bone chain behave like an actual chain. The endpoints would remain anchored (probably as IK modifiers pointing to locators) and I could drag one bone around and have the other, non-anchored bones follow until the chain segment became taut.
However, since that wasn't the effect I was going for I neglected to write down the configuration and merely considered it an amusing accident. Now I want to use that kind of rig, but I can't remember what I did.

I've tried numerous times to recreate this, but to no avail.
Has anyone else built this kind of a rig, and if so, do you remember how you did it?
I did it using 5.1 Pro.
Thanks!