«لَا صَنْعَهْ وَلَا اسْتَادِيَّهْ»

The saying describes a person who lacks any usable skill. Such a person has no trade they can practise well enough to produce work themselves, and no seasoned expertise that would let them guide or instruct others who do the work.

By denying both roles at once, the doer and the master craftsman or supervisor who directs others' work (not an academic professor), the phrase leaves the person with no useful function at all. It works as a sweeping dismissal of someone judged incompetent in every practical respect.

Use it as a blunt judgment about someone who claims competence but can neither do a job properly nor direct anyone else in doing it. It fits complaints about an unreliable worker or a self-styled expert; addressing it to someone's face is plainly disparaging.