I have 3 1400 rails and an 800.
I leave 2 of the 1400's joined the whole time. But to align them, simple put another rail upside down and hold it firmly with your hand at the joint. I can be within a 0.5mm pencil line across the 2800mm and it only takes a few seconds.
TXS, TSC 55REB, CTL Midi, BHC 18, C18Li, T18+3, PSC 420EB, Kapex KS120 EB, OF1400, EHL 65 EQ, ETS EC150/5, RO150 FEQ