Chasen (Cha-sen) is a type of traditional tool for making matcha, especially for preparing ceremonial grade matcha. With this tool, you can break the clumps easily and give you a much smoother and sweeter taste.
百本立 means hundred bamboo strings (or teeth) which are carefully cut by masters and wrapped with cotton string. This technique hasn't changed since around 1400.
(I was very lucky to witness the whole process from zero!)