Lap Steel and B m7b9
No bar position in CEGACE spells B m7b9.
B m7b9 spells B – C – D – F# – A, but the lap steel chair has no bar for it: at every fret of the CEGACE neck, and on every short slant, the strings that land on its tones leave one out or too few of them ring.
In a country arrangement that is an ordinary night's work — the lap steel plays the part of the chord the bar can reach, or a single-string line through it, and lets the guitar and the rest of the band carry the chord. This page draws no grip a steel cannot hold.