The story of mankind is one of doing as little work as possible. And that plays out most excellently as Christian Bale lookalike Primitive Technology seeks to build the most efficient “forge blower” he can with the bounty of the forest.
He starts with something similar to a fan: two intersecting pieces of bark with a stick as a shaft. Rubbing it between his hands does seems to add more oxygen to the fire outside his hut, but it’s too much effort without enough return.
So he breaks out the clay and builds a little enclosure for the fan apparatus. Now the air is directed in a steady column, but it’s still not good enough. So a structure is built to hold everything in place and then, using another stick and some home-made twine, the entire thing is powered by a bow. Clever. Low-effort. Effective.
Back in our hunter-gatherer days someone probably would have called this guy lazy and entitled because back in his day they didn’t even have fire. Progress is beautiful.