equivalent to the canary in a coal mine). (25) [For a detailed
        
        
          step-by-step see my 
        
        
        
        
        
           video]
        
        
          
            The Shoofly
          
        
        
          The centerpiece scene, the shoofly, shows a temporary track
        
        
          running on a dirt berm around the site of workers replacing an
        
        
          old wooden trestle with concrete abutments for a new girder-
        
        
          deck bridge (26).