Kilt Pins are both decorative and functional. They are generally not divided into categories of casual or formal, like some other accessories. They look nice, and they add some weight to the front apron of your kilt to keep it from blowing in the breeze... The kilt pin is worn on the bottom outside corner, on the front apron of your kilt. It should only be pinned through the outside layer of fabric, or it will bunch up funny, and possibly tear your kilt!