Whether you call them slides or beach sandals, nothing says casual summer louder than flip-flops. They are the closest you can come to walking barefoot. These so-called string bikinis for the feet are free in the back so that, when you walk, you hear a sort of soft thwick-thwack sound. So what if they offer no protection and little support—they are guaranteed to be stylish, affordable, and comfortable. Test your knowledge of this harbinger of fun days ahead.