Genkō yōshi

(or "genkoyoshi") is a type of Japanese paper used for writing. It is printed with squares. There are typically 200 or 400 squares on each sheet. Each square designed to accommodate a single Japanese character or punctuation mark. 
"Genkō yōshi" may be used with any type of writing instruments pencil, pen, or an ink brush.
"Genkō yōshi" is used for vertical writing. On a sheet of "genkō yōshi", there is no pre-determined order; there is instead a system of space, which can be designed freely.
One page of Japanese with 400 characters generally equals 225-250 words in English. In other words, an essay of about 10,000 words would be the same as 40-45 "genko yoshi".
History.
"Genkō yōshi" came into common use in the Meiji period. Newspapers and magazines needed to count characters.