Moving away from silhouettes briefly, I'm now looking at the evidence of where skateboarders have been such as the scratches on benches and handrails from grinding, marks on the ground, etc.  Here are a few pictures I.ve taken so far.  There's more to come.

I tried making a cast of the surface of the ledge, however since I can't bring the ledge into college with me it proved to be difficult to achieve.  I tried it anyway, making a clay mould and doing my own carvings, then pouring the surface over with plaster.  This was the outcome, I don't think it worked though.

I will make more moulds such as this one in the foreseeable future and see if I can get some convincing markings without the ledge being with me in the plaster room.