# File karel/world_maker.rb, line 212
    def drop_item(x, y)
      canvas = $window.canvas      
      avenue, street = scale(x, y)  
       if(street < 1 or avenue < 1 or street > $window.number_of_streets() or avenue > $window.number_of_streets()) 
        return
      end
     $world.place_wall_east_of(street, avenue)
    end