Passage: At age 17, Lam became a stuntman and martial arts coach at the Shaw Brothers Studio. Due to his slender build, he was often called upon to substitute female actors. He received $HK60 a day, $HK20 of which went to his master, and another $HK20 he took home to his parents. Lam used the remaining money to treat his brothers to snacks. Lam once mentioned those were his happiest days in his life.

Question: Who did Lam substitute as?
female actors