The BAL X-Chock is our favoirte chock for dual axle vintage trailers.  It is durable and incredibly effective at chocking your tandem, while also dramatically reducing bounce and jiggle movement when using your trailer.  Simply place one chock between the two tires on each side of your trailer. Hold in place with the X-Chock's handle while you turn the nut on top of the chock with a 3/4" ratchet wrench.  The wrench is included so it's ready to go out of the box.