Registration
The exact lining-up of each colour layer in printing, so that the image is sharp.
Also: register, misregistration
In colour printing each ink is laid down separately, and they must land in exactly the same place. When they do, the print is in register. When one is slightly off, edges show coloured fringes and the picture looks blurred. Printers check this with small cross-shaped targets printed outside the image area, called registration marks. Designers allow for small errors by slightly overlapping neighbouring colours, a technique called trapping. In hand block printing, slight misregistration is a sign of handwork and part of its charm.