Refers to where you and another male friend are "group-spooning" with a nice gal on the beach or in bed, and she has her "lower" arm/hand (i.e., the one from the shoulder that she's lying on) extended out in front of her and the dude whom she's spooning is contentedly clasping this hand. So of course you therefore wish to hold her "upper" hand, but the prob is that this would ordinarily oblige one of you to rotate your wrist an entire half-turn to position your hand palm-upwards, which would likely cause a somewhat-painful wrenching of your wrist. So instead, you both twist your wrists just a quarter of a turn so that your palms are facing each other, and then interlace your fingers.
My buddy and I were having a nice long group-spoon with Tiffany as a reward for our assisting her around the house for a few hours, and I ended up spooning her from behind. Well, naturally, I wanted to hold her hand, but it would have been too painful for either of us to turn our hand upwards --- especially after the strenuous housework-exertion that we had all just been through --- so we performed a wrist-twist compromise and thus were able to happily clasp hands all the same.