The bedsheet format (also known as large pulp)[1] was the size of many magazines published in the United States in the first quarter of the 20th century.
Magazines in bedsheet format were roughly the size of Life but with square spines.
[2] Dick Eney's Fancyclopedia II gives the following entry: The first science fiction magazine, Amazing Stories, was published in a bedsheet format.
Later, most magazines changed to the pulp magazine format, roughly the size of comic books or National Geographic but again with a square spine.
Now, many magazines are published in digest format, roughly the size of Reader's Digest, although a few are in the standard roughly 8.5" x 11" size, and often have stapled spines, rather than glued square spines.