In an article at printmag.com, design artist and critic, Steven Heller, claims that the cutoff-torso-spread-leg framing device is possibly the most frequently copied trope ever used. In fact, Heller calls it a "design virus"; one that persists to this day. He names it the "A-Frame".
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As usual, I couldn't leave well enough alone, and had to start dissecting the reasons why this is so prevalent.
According to one source, "a woman’s legs in the A-frame position usually connote domination and empowerment over a puddle of males, and lots and lots of sex". Sounds reasonable enough - you don't have to think too hard to arrive at the conclusion that a close-up of a faceless woman's legs, spread apart, must have some sexual connotation.
image source
Read on if you'd like to check out a gallery of the "A Frame" and other images that come close. This being Retrospace, these are all vintage pictures; however, you can find just as many contemporary examples quite easily.
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These next two courtesy Epiclectic