The 24 sheet normally measures 246" x
108", and is used mostly for billboard advertising, although some are placed
on the sides of large buildings. They come in a number of pieces and are
placed together like a puzzle. Their artwork is designed to catch the attention
of motorists as they drive by. They are issued primarily for major motion
pictures. It got its name from the fact that it is approximately 24 times
the size of a one sheet.
Here's a sample 24 sheet:

HISTORY
The world’s first 24 sheet was displayed
at the Paris Exposition of 1889 and the Columbian Exposition in Chicago
in 1893 by Morgan
Litho.
It was very quickly adopted for all types
of advertising, especially for the circus, and traveling shows.
Movie studios began utilizing billboard
advertising around 1915. The use of this type of advertising occurred around
the same time that movies grew from two to five reels.
Movie studios still issue billboard-size
paper in limited numbers, primarily as 24 sheets and 30
sheets.
AS A COLLECTIBLE
Very few 24 sheets are available in the
movie art collectors market. There are printed in limited numbers. Since
they are used outside, most of them are destroyed when they are removed
from the billboard. Thus, it is rare to find 24 sheet that is intact unless
it was never actually used on the billboard. There are very few collectors
who handle this size because it is so large. The 24 sheet has been used
as murials in clubs and large halls.
For a list of images of 24 sheets in the
MoviePosterDataBase, click here