Hammer-axe tool, available at the right or by pressing 3, allows you to damge and destroy junk blocking you patch, picking up objects or gathering resourse from trees and stones. You have to close the Book of Challengers first, of course. Objects have different amounts of healt, so bigger and heavier things can take a couple of hits! To switch back to your hands, just press 1. By the way, to speed up your chopping and smashing, you can hold the mouse button until a "!" appears. Such a heavy hit makes chopping much faster, but at the cost of additional stamina drain. There is no drawback in terms of losing resources when performing heavy hits over many normal ones.