guitar chord
C♯dim7
Three minor thirds stacked. The seventh is doubly diminished, which is why it is written with a double flat.
Written the other way round it is D♭dim7 — the same twelve keys on a piano, a different piece of notation.
Every fingering that fits a hand
x45350
hard
x45056
hard
x45320
hard
x4535x
hard
9ab9b9
hard · barre
What is true of it
C♯dim7 is C♯, E, G and B♭ — 1, b3, b5 and bb7 counted from C♯.
The easiest of the 5 fingerings below is x45350: 4 fingers, held at the 3rd fret.
None of them uses an open string, so this chord moves up the neck unchanged — the same shape 1 fret higher is the chord a semitone above.
1 of the 5 need a barre.
1 string stays silent.
Where its notes are on the neck
The brass dots are C♯, the root. Everything else is a chord tone with its degree printed in it.
With a different note underneath
C♯dim7/E
012020
C♯dim7/G
312020
C♯dim7/B♭
x12020
An inversion is the same chord with a different note lowest. The name changes to a slash name because the bass is what a listener hears as the foundation.