Most moveable 7th chord shapes also follow the five basic forms found in chords containing open strings, i.e. C7,A7, G7, E7 and D7. The first position C7 chord below can be described as a C7 form. If you damp out the 1st and 6th strings, this form becomes moveable, e,g. if you move it to the 6th fret, it becomes an F7 chord which would be described as a C form of an F7.