Banjo Gdim chord (Open D)G diminished on the 5-string banjo: 5 4 4 5, and 2 more shapes

Frets, string 4 to string 1: 5 4 4 5 (from the 4th fret)

1. String 4 (D): 5th fret, middle finger, G
2. String 3 (F♯): 4th fret, index finger (barre), B♭
3. String 2 (A): 4th fret, index finger (barre), D♭
4. String 1 (D): 5th fret, ring finger, G
5. String 5, the short f♯: open, F♯, not in the chord

Sounds: G B♭ D♭ G  ·  Gdim is G, B♭, D♭ (1 · ♭3 · ♭5)

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

The 5th string: the short f♯ rubs against the G in this shape, a semitone away: some players let it ring, some skip it.

With a capo: on the 5th fret it’s 0 2 5 3 (frets counted from the capo), an open Ddim shape. Spike the 5th string at the 10th fret to keep it in tune with the capo.

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