1. The problem statement, all variables and given/known data I want to attach a metal rod in between a stretchable spring to build my horizontal spring launcher but I have no idea how to attach one or even if design would be possible. 2. Relevant equations 3. The attempt at a solution I was thinking of a design http://i.imgur.com/I0I3X.jpg, but I don't think that it would be ... "firm" or stable.