The black seaweed wrappers used in makimono are called nori. Nori is a type of algae, traditionally cultivated in the harbors of Japan. Originally, algae was scraped from dock pilings, rolled out into thin, edible sheets, and dried in the sun, in a process similar to making rice paper. Whereas in Japan, nori may never be toasted before being used in food, many brands found in the U.S. reach drying temperatures above 108 °F (42 °C).
Today, the commercial product is farmed, processed, toasted, packaged, and sold in standard-size sheets about 18 by 21 centimetres (7.1 by 8.3 in). Higher quality nori is thick, smooth, shiny, green, and has no holes. When stored for several months, nori sheets can change color to dark green-brownish.
The standard size of a whole nori sheet mentioned above influences the size of maki-mono. A full size sheet produces futomaki, and a half produces hosomaki and temaki. To produce gunkan and some other makimono, an appropriately sized piece of nori is cut from a whole sheet.
When making fukusazushi, a paper-thin omelette may replace a sheet of nori as the wrapping. The omelette is traditionally made on a rectangular omelette pan (makiyakinabe), and used to form the pouch for the rice and fillings.