You mean the piece where there's a vertical black cylinder inside? (Attachment shows a older FI F150/Bronco system - the pre-1989 Ranger system is overall similar.
The unit on the right is a tiny fuel reservoir that helps the in-tank lift pump keep up with the high-pressure rail pump. Depending on the year and/or owners that have messed with it it may have a cannister filter in there. There is a shield that mounts to the rail and makes it hard to get to/see the connections on the reservoir (aka accumulator). There are 2 bolts on the top and bottom of the frame securing the shield - I suggest eliminating the front top bolts (goats to get at) and undoing the bottom bolts when you are working on this - the shield can then be swung aside for access and then bolted back at bottom when you are done.
The lines attach by pushing on and off the barbs at the cannister/pump/front filter and are secured by plastic hairpin H-clips. The clips are designed to be replaced each time, and will probably get wrecked when you remove them with screwdriver/piers anyway.
If you have dual tanks, there will also be a switching valve on the rail upstream of the reservoir - similar connectors.
If you are referring to something else on the fuel lines running along the rail, hopefully this will clarify what you are NOT referring to!
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