How to get two base flanges to merge

I rarely use sheet metal commands but need to learn more about them. I am trying to build a part by creating two base flanges and merging together. The problem is I do not have the merge checkbox. Normally I would simply use extrusions but I would like to get a flat pattern out of this. Obviously I am doing something wrong. Should I take a different approach with this part?

Solidworks 2013 SP1

SolidworksSheet Metal