I understand the grammar in this example...
Est-ce que tu sais marcher sur les mains ? - Non, je ne sais pas le faire.Do you know how to walk on your hands ? - No, I don't [know how to do that].But the lesson goes on to say...Note that in many such cases, you add the neutral verb faire to refer to an action.It would be good to have a bit more guidance on which cases require the addition of faire. Is it compulsory in some cases? Is there a rule?