Banjo Ddim chord (Open D)D diminished on the 5-string banjo: 0 2 5 3, and 3 more shapes

Frets, string 4 to string 1: 0 2 5 3 (open position)

1. String 4 (D): open, D
2. String 3 (F♯): 2nd fret, index finger, A♭
3. String 2 (A): 5th fret, little finger, D
4. String 1 (D): 3rd fret, middle finger, F
5. String 5, the short f♯: open, F♯, 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 f♯ rubs against the F in this shape, a semitone away: some players let it ring, some skip it.

Open D tuning: f♯DF♯AD, the short 5th string first, then strings 4 to 1.