What is true of it
F♯dim7 is F♯, A, C and E♭ — 1, b3, b5 and bb7 counted from F♯.
The easiest of the 1 fingering below is bcbc: 3 fingers, one of them barring the 11th fret, held at the 11th 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.
Where its notes are on the neck
The brass dots are F♯, the root. Everything else is a chord tone with its degree printed in it.
With a different note underneath
F♯dim7/A
2323
F♯dim7/C
5320
F♯dim7/E♭
8989
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.