An etrack bar at the floor in front of the front and back tires and behind the rear tires as well as one across the front at the bumper if you are lucky enough to have it at the right level. Set the parking brake hard as well. That should hold it against all but the craziest of driving and/or a crash. Nothing would be enough in that case.
Leo Bricker, 73's K5LDB, OOIDA Life Member 677319
Owner, Panther trucks 5508, 5509, 5641
Highway Watch Participant, Truckerbuddy
EO Forum Moderator
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Support the entire Constitution, not just the parts you like.