Dave. "Ride the blinds" must be more specific, because there is the phrase "ride the rods" too. Mississippi John Hurt in his song "Casey Jones" has Casey instructing the brakeman fix it so the hobos can't ride the blinds. "Let them ride the rods and put their trust in god." (or something similar) he says. I suspect that riding the blinds means getting inside a boxcar while riding the rods means riding outside--either under or between cars.

Murray