Root on A string
no fifthx-13-12-13-12-x
B♭7♭9 is the B♭ dominant 7 flat 9 chord. Its notes are B♭, D, F, A♭ and C♭. It is the same chord as A♯7♭9. A compact four-finger grip without the fifth. Try it as V in a minor key.
x-13-12-13-12-x
Numbers show frets from the low E string to the high e string; x means don't play that string.
Every B♭, D, F, A♭ and C♭ on the first 12 frets. The filled dots are the root, B♭. Build your own shape from any nearby group.
Other B♭ chords
Other dominant 7 flat 9 chords