Underwear over Leggings (like superman)
In game some of underwear i use for my sims, both CC and EA, will show up on top of any leggings that are also worn, superhero costume style. But there are some other CC underwear options that i have where this doesn't happen.
I've tinkered around in S4S but i can't affect any changes or tell what it is that specifies what 'layer' a clothing option is assigned to. If someone could explain what determines this, and how to edit it, that would be great.