Right way: Cross the chains before you attach them to your tow vehicle. They should hang a few inches below the tongue, not drop near to the ground. In the event that your trailer comes of the hitch ball as you're moving, the crossed chains are meant to help cradle the trailer tongue until you can get stopped.
Wrong way: Chains hooked without the criss-cross, and hanging low to the ground. With this configuration, the trailer tongue is guaranteed to hit the pavement, dig a furrow, and do worse things than that after coming off the ball of a tow rig going at speed. You won't get the chance to slow down before your trailer becomes a dead-weight anchor that could jerk you right off the road.
Further reminder: Always double-check your coupler lock before you depart on a trip, and at every stop.
Stay safe!
