A diagonal lattice pattern that creates a grid of diamond shapes. Two major versions of the pattern exist, one version where each (or some) of the diamonds shapes have center lines and small "crosses" in the center, and one version where the grid is created with double lines and empty diamonds.
It often consists of double (or triple) lines for the main diamond grid with a single centerline. The crosses can be either plus signs or small petal-like shapes.
The pattern can be used as-is as a background or in combination with different elements. Sometimes combined with other designs filling adjacent diamond shapes.
Not to be confused with the hanabishi pattern.
Supposedly named after a Heian period poet (在原 業平) who liked the pattern, and popularized by a famous Kabuki actor in the Edo period. Koushi (格子) means lattice in Japanese.