The Coital Alignment Technique is a modification of the nice traditional missionary position. The technique is designed to combat the lack of clitoral stimulation reached in mish.
Less than 15% of women can achieve orgasm from straight up penis in vagina boning. If you don’t believe this low percentage it’s because you’re a boy and you’ve been lied to.
Clitoral stimulation is key to most women achieving orgasm, and CAT is a good way to get there. The technique even has clinical support, including one study published in the Journal of Sex and Marital Therapy, which reported a 56% increase in women's orgasm frequency when using CAT.
The gist of it is, the mans pubic bone should come in to contact with the clitoris, so that while he's pumping, the clit is constantly being stimulated.
It's pretty simple, but here is a lovely instructional video if you need it.