Billhook is traditional clearing tool in Finland and typical model have around 20cm blade which ends into hook that works also like small scythe (pull cut). Mostly I use that hook for moving cut branches away and it also protects blade when you cut near ground (hook hits ground when blade is untouched).
There´s one and two handled model and it´s very handy for clearing saplings and even small trees aswell as general purpose bladed tool for all kind of heavy woodcutting.
Novadays Fiskars made some 95% of billhooks in Finland and it´s modern glassfibrereinforced plastic handled with teflon coated blade. It´s great and strong tool, but not so traditional. There´s still makers of traditional billhooks and here are few:
Metallituote Saarela Oy
You can also find often very good old handforged billhooks from fleamarkets, huuto.net (like ebay).
Here´s one I just got for 15€: