On this day in 1942 Erico Fermi created the first nuclear chain reaction. However people had chain reactions long before that -- and have had them and ever since. We reacted whenever a chain we were using (to pull or secure something) snapped and came apart; or when the going got rough; or when we just had two chains that weren't long enough. Those days were gone quick as a wink when we learned to fix the weakest link. Here's how. When a link breaks, a quick repair can be made by joining the weakest link back together with an ordinary padlock. The same goes for joining two or more short sections of a chain together. Another option is using a large nut and bolt. Either way it's only make-do at best, but will do until you get a proper connector link or a new chain. And that's the On The House tip for today.