There is a difference in Japanese and Chinese in printing typefaces for this radical. In the Kangxi Dictionary and in Japanese, a short vertical line on top of the horizontal line is used. In China, Taiwan, and Hong Kong, a slanted dash, or Radical 3, on top of the horizontal line is used.
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.