The Collaborative International Dictionary of English v.0.48:

maulstick \maul"stick`\, maul-stick \maul"-stick`\, n. [G.
   malerstock; maler a painter + stock stick.]
   A stick used by painters as a rest for the hand while
   working. [Written also mahl-stick and mahlstick.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

maulstick
    n 1: a long stick that a painter uses to support the hand
         holding the brush [syn: maulstick, mahlstick]