Here are some useful movable minor seventh flat five chord shapes, shown as Gm7b5. The fifteen shapes shown here are commonly used voicings made up of various string combinations, but you could use the formula to work out all possibilities on groups of four adjacent strings, as well as other possible fingerings. Experiment!
Minor 7b5 chords are commonly used in minor keys as shown here.
A diminished 7th chord is created by flattening the 7th degree of any minor 7 flat five chord. Because the 7th is already flattened, it becomes a double flattened 7th. For example, a C dim7 chord contains the notes C, Eb, Gb and Bbb (1, b3, b5 and bb7).
A double flattened seventh is the same as a 6th degree (e.g., Bbb = A). It is referred to as a double flat 7 because the chord is technically a type of 7th chord.
The following diagrams show some common open diminished 7th chord shapes. Diminished 7ths are commonly just called diminished chords and are usually played instead of a diminished triad wherever a diminished chord symbol occurs.