By Kayla Kibbe From the secret to hitting the G-spot (pressing down on their stomach) to the most dangerous sex position (reverse cowgirl, allegedly), TikTok is home to a vast trove of (often dubious) sex advice. The latest sex hack to take over the platform? Knee stuff, apparently — by which I mean use of a well-placed knee to stimulate the clit. According to TikTok, “the knee thing” is the must-know foreplay technique for anyone who has a clitoris or has sex with people who do. Most likely taking place during a pre-coital makeout session, the knee thing involves one person positioning their …