A non-standard term (sorry, Tony) to describe a strap with a positioning guide, which sits between the child’s legs on a booster seat, like a crotch buckle would on a harnessed car seat. This positioning device helps to guide the lap portion of the vehicle seat belt off the child’s abdomen and instead low, across their hips, to help achieve proper seat belt fit and prevent “submarining”. TLDR version of “submarining”: a child slipping forward and/or out from under the lap portion of the seat belt in a sudden stop or crash.