The extra screw terminal is attached to something I fabricated. I cut a rectangle shape with tin snips from 1/32" thick copper sheet and drilled two holes in it. One hole mounts it to the battery post clamp bolt and the other hole holds a screw for the extra terminal. If you prefer you could just use a crimp connector with a larger ring hole and put it directly on the clamp bolt.
Carter with Patty from Kirkland, WA
'01 Southwind 32V - F53 V10 with '12 Ford Focus automatic 4 down & US Gear aux brake