Radical 24 meaning ten, complete, or perfect is one of 23 of the 214 Kangxi radicals that are composed of 2 strokes. "十" is two crossed lines. It was originally a vertical line, a pictogram of a needle (now 針), later supplemented by a dot in the center of the stroke which became a short cross-stroke and expanded to the current shape. In the Kangxi Dictionary there are 55 characters (out of 40,000) to be found under this radical.
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.