In this age of acronyms, FMLB or LMFB (or do you say FBLM?) are favorites in the power supply world.
‘First mate last break’ is a feature that provides for a longer than normal power blade or signal pin. Typical uses are i.e., as a long, or first mate, power blade for grounding the system before the hot power blades are engaged. Or a long signal pin may serve as a warning to the system that the power supply is about to be fully engaged and launching watts at its waiting functions. OTOH (on the other hand), ‘last mate first break’ provides a short pin as a possible warning that the system is about to be shut down.
However, I suspect the uses for these varied mating lengths are almost as varied as the possible variations. People have asked me why we advertise our BYO (build your own) power connectors versus just having every configuration available off the shelf. While it may seem an arbitrary decision by TPTB (the powers that be), FMLB illustrates our true rationale.
There are commonly accepted practices among certain factions, but no real standard logic as to where a long blade or signal pin is positioned. Combine that with the sheer volume of possibilities—two to twenty power blades and up to 60 signal pins. IIRC (if I recall correctly) going back to factorial equations from college days, the result would be such a heap of potential combinations it would make MEGO (my eyes glaze over)!