Guitar chords in the key of G:
G Am Bm C D Em F#dim

Chord Gdim7 notes: G, Db, E and Bb. You must leave out the 2nd and 1st strings.

Gdim7 - G diminished seventh guitar chord's alternative names: G°, G°7, Go7, G7dim. See also: Gdim and Gm7b5.

Steps: 1-b3-b5-6(or bb7).
1(G), b3(A#/Bb), b5(C#/Db), 6(E).