There are lots of ways we catalog memories from life in a physical sense. That's how we get memorabilia. I've loved seeing how PCT hikers create their own memorabilia to look back on later in life. Obviously, for me it's a photo narrative. For Butters though, it's autographed baseballs. He has each thru-hiker he sees sign the baseball. When the ball is full, he sends it home and gets a new ball. What a cool way to capture a piece of each thru hiker to reminisce about down the line. 

Cheers, 

Jonathan