The Collaborative International Dictionary of English v.0.48:

Cockshut \Cock"shut`\, n.
   A kind of net to catch woodcock. [Obs.] --Nares.
   [1913 Webster]

   Cockshut time or Cockshut light, evening twilight;
      nightfall; -- so called in allusion to the tome at which
      the cockshut used to be spread. [Obs.] --Shak. B. Jonson.
      [1913 Webster]