Standing on the ledge
The novel opens with Finch and Violet standing on the ledge of the bell tower, both contemplating what it would be like to jump. They meet during this vulnerable moment, forging a deep relationship thereafter. From then on, there are several repeated images of them standing on a ledge—or standing on a high point—like when they're on Hoosier Hill, on Purina Tower, on the edge of the Blue Hole. With each new height, they are reclaiming the image for themselves; they aren't trying to die, they are trying to live.
Holding breath underwater
Since water is a recurring motif, and suicide by drowning lurks in the novel's pages, the image of Finch holding his breath underwater is a powerful one. We see it twice, essentially the exact same image. First, we see it when he is taking a bath because the weather is too bad to run, and he submerges himself under water thinking about the world record for holding breath, and how he has done it for five and a half minutes. He think of Woolf, and then he bursts through the water, gasping for air. The second time, he and Violet are at the Blue Hole. He tells her he is going to look for the bottom again, and he stays under for a long time, relishing the weight of the water on top of him. Eventually, when he resurfaces, we see the same thing as before: Finch surging upward, gasping for air.
Finding the "your turn" rock
The "your turn" rock that Finch gives Violet at the beginning of the project is a provocation to her to return to the world of the living, to let go of the world of the dead. He wants her to choose where to go next, wants her to have agency. When Finch finds it in his locker, he understands that Violet accepts his plan—whatever that plan is—and he, too, feels like he can go on living. At the end of the novel, when Violet discovers Finch's body after he died, she finds the rock in the pocket of his jeans. She said herself that Finch would want her to be the one to go there, and given everything else he planned to keep communicating with her after he died, it makes sense: the rock is hers forever now, it's her turn to go on living.
Running
There are some striking images of Finch running, sweating, legs pounding, lungs heaving, pushing his body beyond the point of what seems possible. He runs in inclement weather, he runs late at night. The day he gets the flowers for Violet, he ditches his car somewhere random and runs so hard and fast he's basically taunting his body to give out. He starts to worry if he locked his car door, and that makes him run harder. The image of him running as fast as his can—his whole body pushing to its limit—in no direction, into the middle of unknown farmland, seems to make tangible what he is experiencing in his mind. Finch is trying desperately to go, to go anywhere but here, to escape some thing he can't get rid of. It's an image of strength (he runs six miles at that speed, totally unprepared), and also of desperation—it seems he would run to the end of the world to make the feeling go away.
