The work above is one of my favorites of Beever's. It covers up the depth of the bench against the pavement to make the snail appear to be crawling onto the bench. The use of shadow and overlapping of the snail on the bench makes the eye perceive the snail as in front of the bench, and in continuation, the pavement drawn portion must also be before the bench. This uses the eye's ability to create slight discrepancy between real life and perception, in order to portray an image that "makes sense". The shadow is also covering up a real reflection of a store's lit sign on the bench, as the chalk material is not reflective, and Beever used lighting in his chalk drawing to make it appear as though the top of the snail is reflecting the store sign.