Lenny gets up.
This is the first time Lenny has done this in quite a long time. Within the wasteland that is the Fourth Wall, there's not much to do except sit there.
Lenny looks around. There's not much to see except blankness and the thin, purple ground. In the distance, he sees the horizon line. There is one on both sides, left and right. This means that there's just more nothingness beyond, so the Fifth Wall couldn't be on the left side, nor the right side.