I have to make a dual blackboard like the one here, http://www.ucd.ie/physics/lhcb/contact/blackboard.jpg,
My biggest concern is what sort of mechanisms I should use to allow for smooth and easy movement of the blackboards. The boards need to be brought up and down, and be able to stay in place once they've been moved.
I do have an idea on how to do it with weighted cords and pulleys, but I believe there are people with more experience in this area. I'm not as certain about the mechanisms to keep the boards in place though.
Can someone help identify the parts I need to make one of the board to move up and down? Also, which parts do I need in order to make the boards stay in place after being moved?