can stay home and work on some research for his job at the grocery store. And when the sheet of paper containing his notes flies out the open window, he foolishly chases after it; the dangerous excursion out onto the ledge of the apartment building makes up most of the story, and Tom nearly gets himself killed.

Eventually, he's trapped outside on the ledge, unable to reopen the window, and wondering if he'll lose his balance and die before anyone can rescue him, when he starts emptying his pockets of everything except that paper of notes that he was able to grab. He throws away meaningless letters and useless coins. And there's nothing else in his pockets that would help people identify his body if he were to fall and die on the concrete far below. Tom is empty, then, in a figurative way as well: he's wasted his time at work, and all that people will find on his dead body is an "incomprehensible" sheet of notes. Even this project he's been working on doesn't matter, he realizes.

Let's take a look at the passage where Tom realizes all this, when he understands how he's been living his life in an empty way:

He wished, then, that he had not allowed his wife to go off by herself tonight--and on similar nights. He thought of all the evenings he had spent away from her, working; and he regretted them. He thought wonderingly of his fierce ambition and of the direction his life had taken; he thought of the hours he'd spent by himself, filling the yellow sheet that had brought him out here. Contents of the dead man's pockets, he thought with sudden fierce anger, a wasted life.

Happily, we realize that Tom has changed and that he will change the way he lives his life from now on when he breaks the window, safely reenters the apartment, and allows even the yellow paper to fly back outside as he laughs and heads out to join his wife. He's going to fill the emptiness of his spirit by recognizing what's really important to him: his wife, not the potential money he might make by being recognized and promoted at work.

In "Contents of the Dead Man's Pocket," the phrase "sheer emptiness" refers to the absence of a handhold. Tom, out on the ledge outside his apartment window, has retrieved the paper he wanted and is moving back along the ledge towards his apartment. He is physically tired but also mortally afraid. At this point he knows the "slender hold" he had on his mind was "going to break," and he would give in to fear and fall. He begins to take rapid steps along the ledge without thinking, fingers reaching out across the brick for tiny handholds.

It is in this frame of mind—in desperate fear of giving in to his fear—that Tom, reaching out to find another groove in the brick, instead finds nothing. This "sheer emptiness" is of course the open window to his apartment. Had Tom been in a better frame of mind, he would have realized this and not be surprised. But he had been moving without thinking, even keeping his eyes closed. In a way, all his concentration was focused on not being afraid, rather than on getting back to the window. Because he is surprised, he reacts badly, stumbles, and causes the window to fall closed. It takes all his powers of concentration to master his fear enough to finally break the window and escape to safety.

In Jack Finney's short story "Contents of the Dead Man's Pocket," in the lines in question, Tom has just overcome his fright enough to bring himself to cross back from the ledge of the one building where the paper had come to rest back to the ledge of his own building. He has also brought himself to start very slowly edging his way along his own ledge back to his window sill by taking "dozens of tiny sidling steps" with his "chest, belly and face pressed to the wall." As he moves along, he uses his fingers to feel along the brick facade of the building, which helps him keep moving in the right direction and helps him maintain his handhold on the bricks.

However, in the lines in question, he also makes the mistake of letting one "fraction of his mind" realize he is going to fall, which makes him panic. As he panics, he starts taking steps more rapidly without patiently feeling for what he's doing. As he keeps scrambling along the brick, he keeps letting his hands slide forward until his "left hand slid onto not brick but sheer emptiness, an impossible gap in the face of the wall," which makes him stumble. The "sheer emptiness" is explained in the next clause--the emptiness is a "gap" or hole. By "gap," we can assume that he simply means there is a large space in the brick's mortar caused by wear and tear. He is probably also using hyperbole, meaning exaggeration, to describe the gap in the facade because it startled him so much. However, had he been going slow enough, he would have been able to feel around the gap and would not have lost his balance.

As a result of being startled by the gap, he stumbles, staggers, and starts to fall but breaks his fall by clawing at the glass and wood of his window pane and window sill.