Banjo Bdim chord (Open G)B diminished on the 5-string banjo: 3 4 3 3, and 5 more shapes

Frets, string 4 to string 1: 3 4 3 3 (first position)

1. String 4 (D): 3rd fret, index finger (barre), F
2. String 3 (G): 4th fret, middle finger, B
3. String 2 (B): 3rd fret, index finger (barre), D
4. String 1 (D): 3rd fret, index finger (barre), F
5. String 5, the short g: open, G, not in the chord

Sounds: F B D F  ·  Bdim is B, D, F (1 · ♭3 · ♭5)

Found in: C major (vii°), G mixolydian (iii°), D dorian (vi°), A minor (ii°)

The 5th string: the short g adds the ♭6 over Bdim, a colour rather than a clash.

Open G tuning: gDGBD, the short 5th string first, then strings 4 to 1.