Radical 17 is one of 23 of the 214 Kangxi radicals that are composed of 2 strokes.
It does not occur as a character on its own. In combination, it historically takes meanings such as "open mouth", "box", "frame", "hole". In contemporary use, it is the base radical of the following characters:
Fazzioli, Edoardo. Chinese calligraphy : from pictograph to ideogram : the history of 214 essential Chinese/Japanese characters. calligraphy by Rebecca Hon Ko. New York: Abbeville Press. ISBN0-89659-774-1.