First, he cut bamboo tubes to various lengths, leaving an extra finger's length on each one.
He pressed the tip of his sharp military knife against the side of a bamboo tube, then used another piece of bamboo as a hammer to strike it down hard, piercing a hole. He then used the bamboo knife to widen the hole, creating a straight, horizontal slit.
He stood the bamboo tube upright and placed the blade vertically against its edge, giving it a light tap downwards.
CRACK.
Due to its natural grain, the bamboo tube split open instantly, cracking all the way from the top down to the slit.
He repeated the process on the other side, easily creating a small window-like opening.
Then he flipped the tube over and made another "window" in the same way. Now he could slot it onto the top of the bamboo wall.
This semi-H-shaped structure allowed one bamboo tube to be slotted securely onto another. If it didn't fit, he'd just whack it a few times with the bamboo knife, forcing it into place.
