Skirts are part of a garment fastened around the waist and hanging down around the legs. While such features can provide very generous cover compared to the rest of a slave girl's outfit, the material itself is often transparent enough to see through. This can provide the slave with a degree of modestly without concealing too much of her body from her master's gaze. They also add a certain air of elegance around slaves, as it accentuates the girl's legs and inner thighs, making them seem sexier.
Popular amongst slave outfits is the split skirt, a design incorporating veils which drape the legs from the front and back; leaving a wide gap at the sides. This allows for some coverage of her inner legs, but only so long as the slave is standing straight and still, otherwise it exposes her private regions for all to see.
Princess Leia's slave bikini also incorporated a split skirt, a feature that she was grateful to have due to the privacy it allowed her. However even broad Lashaa silk veils couldn't completely conceal the fact that Leia was completely bare underneath, having been forced to wear the veils with no underwear. This fact was often the source of crude catcalls and derisions from the men. Technically the skirts fitted to Leia's slave bikini were a design bandaid due to the rigid nature of her gold skirt plates, so the original G-sting was removed to give her the full freedom of movement to her legs, although the removal of this undergarment left her feeling very self-conscious and vulnerable.