Oh, I dunno. In a cargo van, one skid weighing in at 300 pounds, and being up to three feet high, one set of brackets and a 2x4 at floor level is more than enough to keep the skid right where it is. On the other hand, a 1500 pound skid, placed like two feet behind a single 2x4 load bar, giving it plenty of room to build up speed and, yeah, that'll snap a 2x4 load bar in a, well, in a snap. But a skid or two of empty milk crates, a 2x4 load bar or two is all that is needed. Some loads can be secured with 2x4's, some need to be secured with ratchet straps or other tie-downs.
Common sense and some caution should be used when using brackets and a 2x4 load bar. I've seen it happen with 3 or 4 drivers now where they'll get complacent (or lazy) and just use one load bar at floor level for a high skid, or for a top-heavy skid. In a panic stop, it probably won't snap the 2x4, but it can flip right over the top of it.
It thoroughly ruined the driver's day, but one of the funniest things I've ever seen was a driver who had a single drum, 750 pounds, not on a skid. Had it placed a foot or so inside the back door, and a couple of feet in front of that he strung a single e-track strap between the two sidewalls of his 2-week old Sprinter, to keep the drum from flying through the windshield. He loaded just before I did at the shipper, and I questioned his securement methods, but he assured me that he knew what he was doing, as he's done this a hundred times before.
A few miles into the trip he had a panic stop and the drum didn't fly anywhere, but it did slam into the strap, causing the walls to nearly slap together. Totaled the van.
So whether it's a 2x4 or a strap, it must be used properly.
