They can't handle the truth

I don't know what that is, but I'm having enough trouble with the horseshoe to be uncomfortable lol

What it is, is a very old joke.
But yeah, shoe trees are wooden frames placed inside shoes to help them keep their shape. Most look like this: https://jarroldcdn.azureedge.net/products-temp/loake/xtraveltree_travel_shoe_tree_2%7Bw=1000,h=1000%7D.jpg