A player MUST use any two of their four hole cards to make their best low hand. All low cards must qualify (be ranked eight or lower). A card may be used high, as well as low. Example: A two of diamonds may be used to make a diamond flush, as well as fit into a low hand.
Straights and flushes have no value for low. A pot is split between the best high hand and best “qualifying” low hand. If no low hand qualifies, the best high hand will win the entire pot.