What is true of it
Ddim7 is D, F, A♭ and C♭ — 1, b3, b5 and bb7 counted from D.
The easiest of the 1 fingering below is 7878: 3 fingers, one of them barring the 7th fret, held at the 7th 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 D, the root. Everything else is a chord tone with its degree printed in it.
With a different note underneath
Ddim7/F
abab
Ddim7/A♭
1212
Ddim7/C♭
4545
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.