key block (woodblock printing)
Only when written 墨版
In traditional Japanese woodblock printing, the block that prints the black outlines and serves as the registration guide for color blocks.
In making ukiyo-e, the key block is carved first.
key plate; K plate (CMYK printing)
In modern four-color process printing, the plate that prints black ink; also called the K plate.
In CMYK printing, the K plate is often printed last.
Standard kanji spelling for the key block in woodblock printing.
Katakana spelling used in technical printing contexts, especially for the K plate in CMYK.
墨 (sumi, 'black ink') + 版 (han, 'printing plate/block'). The term is used in both traditional woodblock and modern offset printing.