Women's Boyshort (Panties)

A leg is what makes this shape, and no other underwear has one. Rather than stopping at the crease where thigh meets body, the fabric continues an inch or two down the leg and finishes in a straight hem. That single feature is also the one buyers get cheated on, because plenty of pairs sold under the name have no leg at all and are hipsters with a squared-off back. Measure the vertical side seam below the hip, and under about an inch means you are holding something else.

Everything awkward about the shape follows from that straight hem. A horizontal edge crossing the widest part of the thigh has nothing holding it down, so it creeps upward until it finds a narrower place to grip, which on most people is the top of the thigh within an hour. Three fixes exist and good pairs use at least one: a curved back panel with a seam running under the seat so fabric follows the body instead of bridging it, a hem cut slightly longer at the outside than the inside, or a strip of silicone printed inside the hem. Knit with real recovery, meaning it springs back to length after you stretch it, grips skin. Stiff papery cotton slides on it and rides up whatever the cut.

Hipster shares the low rise and the wide side yet finishes at the top of the thigh, so it prints a waistband and no leg line. Brief cuts the leg across the thigh and puts the waist above the hip bone. Bikini removes the leg and half the side together. Bike shorts and slip shorts sold for chafing run longer and tighter and are worn as a layer under a skirt rather than as underwear. Only the boyshort puts fabric between the thighs while still working as a daily pair, and that is the reason to own some.

Dresses and skirts in warm weather make the strongest case, since skin rubbing skin over a few miles of walking is what this prevents. Sleeping, lounging and cold days under trousers follow behind. Fuller thighs are the case where a flat-cut pair fails fastest. The curved rear seam stops being a nice detail and becomes the whole purchase. Skip them under fitted trousers, because the thigh hem prints a horizontal line halfway down the leg, which reads more obviously than any waistband. Humid heat goes against them too, as fabric held between the thighs stays damp.

Flip the pair and study the back: a seam curving under the seat beats a single flat piece every time, and you can see it in ten seconds. Stretch the hem and release it, because a hem returning slowly is a hem that rides from the first wear. Walk ten steps in the fitting room rather than judging it standing still, which is the position it behaves best in. Cool water and flat drying are what keep the hem gripping. A relaxed hem ends the pair, since nothing brings the grip back once the fabric has given up.