PRO clipbox,thick
  
  
  IF N_elements(thick) eq 0 THEN thick=1.0
  
  thick = cround(thick)
  
  c = !P.clip + [-cceil((thick)/2.0),-cceil((thick+1)/2.0),$
          cceil((thick+1)/2.0), cceil(thick/2.0)]

  plots,[c(0),c(2),c(2),c(0),c(0)],$
    [c(1),c(1),c(3),c(3),c(1)],/DEVICE,thick=thick
  
END