The Collaborative International Dictionary of English v.0.48:

Faldstool \Fald"stool`\, n. [See Faldistory.]
   A folding stool, or portable seat, made to fold up in the
   manner of a camo stool. It was formerly placed in the choir
   for a bishop, when he offciated in any but his own cathedral
   church. --Fairholt.
   [1913 Webster]

   Note: In the modern practice of the Church of England, the
         term faldstool is given to the reading desk from which
         the litany is read. This esage is a relic of the
         ancient use of a lectern folding like a camp stool.
         [1913 Webster]