remy:
These are the tensioners that were on the flatbeds of the firm I worked for in the 70’s. A bit crude alongside todays ratchet straps and they were welded in place on the trailer but I forget how many there were.
Remy, we had a slightly different version of those. The base was wider than the the carriers, enabling it to be mounted into a specially folded C channel. The channel was mounted to the cross members, either the full length of the trailer or with gaps above the wheels, depending on the profile of the trailer. A bolt or deformation on the end of the channel prevented the mechanism falling out.
We also had a version called a clip-on, rough sketch below.
Another advantage of the Australian tie rail, over hooks, eh Dig. 
Excuse the napkin drawing.
