We have been borrowing a bridge from another pack for several years. This year, our Webelos2 group (actually 2 dads) built a bridge for our own pack, based on the design of the one we've been borrowing. It doesn't collapse, but it stores small.
I don't have a digital image, so I'll have to draw and describe it.
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These pieces are the supports - really just 2x4's on end. We actually took the end pieces and put them on a slant. One side is red and the other is blue. The red side has the Boy Scout insignia, the blue side has the Cub Scout insignia.
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Now we've added the bridge portion. There are 12 cross pieces representing the 12 points of the Scout law. On the top of each piece is a single word representing a particular Scout Law. The reverse side has the entire law printed on it. Our Webelos 2 den builds the bridge. They hold a cross piece so the word faces out and they read that portion of the Scout Law. When they have finished reading, they put the cross piece onto the bridge. (There are pegs on the supports and holes in the cross pieces). When the scout law is finished, the bridge is built, by those who will be using it. Before each scout steps onto the bridge, the cubmaster (me) and the den leader remove the blue shoulder loops from the uniform. The scout crosses the bridge, and the parents add the red shoulder loops to their uniform. (This year, I'm going to see about getting a scoutmaster or some boy scouts to help with that part.)
Hope this makes sense.