I know these lines....Ford's quick disconnect fuel lines that aren't exactly quick. lol. I fought and fought and fought with both the aluminum one and the X multisize one when disconnecting the incoming fuel line to my fuel rail line when I did my motor swap. Then, all of a sudden, it disconnected.
They should be 1/2" line size. Stick the tool in the groove, push into groove(it should stay in the groove on it's own), push both ends of the line towards eachother, and it should seperate.
'01 XLT disguised as a '03 Fx4 Level II.