Parmenides and the Third Man Argument

Socrates has talked about things sharing in or partaking in the forms, but how should we understand this? Parmenides chastises socrates for being particularly worried about cases like hair and dirt. Then he throws down his first fundamental challenge to the theory as a whole. Socrates makes a nifty suggestion, which is that the form could be present in its participants the way that the same day is present in many places at the same time.