"The vending-machine style, anonymous wank this club provides is too easily seen as a metaphor for sex in our society, yet it forces you to notice what goes on behind the scenes - the picture Maggie hangs up underneath the red button that tells the "customer" when she's ready or when she gets so good at her job that she wanks while reading a magazine. There's Luisa, her colleague who shows her the ropes, who took this job to get away from an abusive husband. And then there's penis elbow. Tennis players get tennis elbow, Luisa explains, we get penis elbow.
Here's the trailer: