Source : Webster's Revised Unabridged Dictionary (1913)

Bedpost \Bed"post`\, n.
   1. One of the four standards that support a bedstead or the
      canopy over a bedstead.

   2. Anciently, a post or pin on each side of the bed to keep
      the clothes from falling off. See {Bedstaff}. --Brewer.

Source : WordNet®

bedpost
     n : any of 4 vertical supports at the corners of a bedstead