Tightening the M&R Products tie-downs. These are attached with M&Rs D-rings at each corner of the trailer. This type of strap wraps around the axle or A-frame to secure the car. Four straps should be used for security. With only one strap on each end, a common practice, the car can shift its weight on the trailer in an emergency maneuver. This gives rise to the phrase, We have lift off.