In the previous episode, the view outside Otis' cell window was shown as a wooden fence, a vine or tree branch and open sky (actually a makeshift fence prop and a stage scrim). Here, the entire view is of a brick wall.
When Andy tries to wake Otis up, he goes to the back of Otis' cell. He grips the iron bar of the window and then knocks on the window as if there was glass in it. There is clearly no glass in the window, as the hand that is knocking is going right through the window and because of his hand gripping the iron bar.