In Chapter 6, what is the meaning of the ladder that Gatsby imagines he sees in the blocks of the sidewalk?

I take note of the reference in the previous response to the horizontal sidewalk transformed in Gatsby's vision to a vertical ladder. And I cannot help but wonder whether or not Fitzgerald deliberately chose to impose upon Gatsby a vision that showed the falseness and hopelessness of the metaphor, since one cannot climb a sidewalk, Monty Python movies notwithstanding, nor become successful moving only laterally. Fitzgerald could just as easily have provided something upward-climbing, for example, a trellis, to trigger the ladder in Gatsby's mind. But he didn't. And I do think that pretty much every detail in the novel was chosen with mindfulness and intent, which is part of what makes this, arguably, the great American novel. While at this point in the novel Gatsby still believes he can fulfill the American dream, the reader has seen many hints that he will not, and this false metaphor seems to me to be yet another of those hints. The American dream, Fitzgerald is telling us, is as delusional as climbing a sidewalk.