The tire swing is commonly used by a lot of characters. What themes or ideas does the swing convey through this?

After
settling in at "Out-With," Bruno gradually starts to explore his new surroundings, but
with no one to play with, he finds himself bored most of the time. To make the time pass more
easily, he builds himself a tire swing. He gets the spare tire from Lieutenant Kotler, grabs
some rope from the garage, ties them together, and hangs them from a large tree.

At first, the tire swing is an agreeable way for Bruno to fight off boredom, but the
fun doesn't last very long...