After riveting the skeleton together, the next trick is to get the skins clamped on the skeleton.

The skins come with pilot holes where each rivet will go, and the real trick is to get them all clamped up so the pilot holes are lined up on the centres of the spars and ribs.

Then you drill through the pilot holes to make the rivet holes in the skeleton. After drilling each hole, you put a cleco in to hold the pieces together temporarily until the riveting is done. All those things sticking out are the clecos.