There may be some debate as to whether Finney's words and phrasing meant to help readers visualize the plot are entirely successful, but one early example of this visualization of the plot is in his description of the curtains reacting to the warm air rushing in from the hall:
Behind him he heard the slap of the window curtains against the wall and the sound of paper fluttering from his desk, and he had to push to close the door.
Then as the moving air stilled completely, the curtains swinging back from the wall to hang free again, he saw the yellow sheet drop to the window ledge and slide over out of sight.
These two sentences are meant to demonstrate the force and direction of the rush of air coming into the cool apartment, with open window, from the warm hall through the open door. We are meant to be able to visualize the curtains being forced by the incoming warm air current--helped by the out-drafting cool air--against the walls siding the windows. With this, we are meant to visualize how the "creased," therefore not flat, yellow paper would move in such a warm current toward the window, "open a few inches."
Whether this works out as planned by Finney is debatable since many readers find they need multiple readings to understand what is happening. Nonetheless, Finney means this to help readers visualize the plot progression because the concept that the yellow paper gets blown out an open window from a hallway draft is a very important plot point.
Words and phrasing that are meant to help readers visualize setting are more often successful and readily comprehended. For instance, the important point about where in the setting the window is in relation to the desk is important to plot and suspense development. In the following quote, this proximal relationship is established. Since the setting in many ways moves the plot forward, like in creating the problem and constituting the external conflict, it is critical to understand the subtleties of the setting in order to follow how events occur and flow into each other.
He got up, ... [and] stepped to the living-room window beside the desk, and stood breathing on the glass,...