If the dowels you are talking about are flush with the wood sides of the bench top, those are the plugs I am talking about. Drill in with a small bit in the center of the dowel and see if you hit metal.
Looks like shop benches in many schools. If you look along the edge you should see some plugs. In your picture it looks like two of the holes have the plugs removed already. Generally is a threaded rod running the width and by removing the plugs you can tighten the rods eliminating the splits.
My dad was left handed, I am right handed, we always fought wrapping each other's extension cords or hoses up as it was reverse what it normally was rolled/wrapped/coiled up as.
My dad had the same set (except) it had a ratchet instead of a breaker bar, 3/8 drive. That sat on top of his workbench at the station and then at home, now in his shop we built before he died. Will try to remember to look at it this weekend when getting my mower out of his shop.
My only concern with the wood covered gutters, it could become a wonderful home for mice. Otherwise, great barn! Good on you for taking on this endeavor.
Built a pole barn on the fairgrounds in 1994. Rollers were some type of plastic/nylon. They got flat spotted from not being used and the sun just beating on the South end of the building. Changed them out and doors move again. Just a thought.
You can get a self governed blade so if the wind comes up while you are sleeping or away, basically if the fan starts going to fast it causes the tail to come towards the fan so the wind "slips" through the blades instead of spinning the blades.
Here is some good information...