Hitchhikers are what I call a form of street art that latches onto signpoles etc., like a lamprey hitches a ride on a shark. Most often they are bolted on, with the bolt ends then hammered down, making them difficult to remove without a hack saw. These often remain up for years. Others survive by being out of easy reach, like the ubiquitous boloed sneakers. In general any unauthorized 3-D street art is welcome here, including 2-D paintings on wood. But this is not a group for pasted paper on walls, nor for 3-D art photographed in galleries or someone's home.
If you are posting a photo of something that doesn't readily reveal its 3-D nature in your photo, describe what is going on in the caption, otherwise I might delete it by mistake.