[Ianworld]

My team had a similar idea in 2005. We had a carriage on a beam system for our tetra manipulator. It ran along an aluminum 2" x 4" square extrusion and at the start of the match we would increase its length by folding up a second 2 by 4. Inside the top 2x4 was a slightly smaller chunk of metal that would drop down and lock the two together, short of going upside down gravity held it in place nicely.