What you are talking about is the junction block which is a fitting integral to the "flex hose" connecting at the intermediate steel brake line, running from the front distribution block in the engine compartment to just in front of, and above, the rear axle. The junction block has a hole in it - top to bottom. This hole (about 3/8ths) is used to mount the junction block to the rear axle tube. The tube has a threaded hole in it. You line up the junction block over this threaded hole (driver's side of car) then use the special Ford fitting. The fitting is actually a breather tube with a threaded end. The threaded side fits through the junction block and threads into the axle tube. The upstream end of the flex line runs up to the steel intermediate brake line. The two joint together at a bracket which is tack welded to the underside of the car. A clip is used to secure the flex hose into the bracket. First hand thread the flex line and steel line together with the fitting on the steel line. tighten with a line wrench, then slide the retainer clip over the bracket and around the end of the flex line, to hold it in place.
CAVEAT!!!! not all breather tubes and flex line/junction blocks are the same. There are two styles - single exhaust and dual exhaust. They are NOT interchangeable. The junction block is thicker, breather tube longer, on the dual exhuast. This positions the angle of the rear steel lines slightly different and also changes the length of each of these steel rear brake lines which run along the axle. If you use a single exhaust flex hose on a dual exhaust setup, the flex line is too close to the driver's side exhaust pipe and will burn/melt through, causing brake failure.
good luck.