Banjo Ddim chord (Open G)D diminished on the 5-string banjo: 0 1 3 3, and 5 more shapes

Frets, string 4 to string 1: 0 1 3 3 (open position)

1. String 4 (D): open, D
2. String 3 (G): 1st fret, index finger, A♭
3. String 2 (B): 3rd fret, ring finger, D
4. String 1 (D): 3rd fret, little finger, F
5. String 5, the short g: open, G, not in the chord

Sounds: D A♭ D F  ·  Ddim is D, F, A♭ (1 · ♭3 · ♭5)

Found in: C minor (ii°), E♭ major (vii°), B♭ mixolydian (iii°), F dorian (vi°)

The 5th string: the short g rubs against the A♭ in this shape, a semitone away: some players let it ring, some skip it.

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