Cut a piece of safety wire and bend or loop it into a "U" shape.
Slip the wire inside the screw housing and on each side of the clamping screw.
Bend the loop end down to conform to the clamp radius. This is done so that as the loop is drawn toward the screw it will slip under the housing and pull tight between the screw and the strap.
Pull the loop into position under the screw and bend one side through the blade screw driver slot in the screw. Then twist the two wire ends until all slack is taken up.
Here one can see how the loop draws in under the screw and over the clamp band. The excess wire has been snipped off.
To remove the safety, snip the wire on each side of the screw head, and then back the screw off. The safety wire will come out of the screw housing as the band comes out.