Hair pins are open and can be used for styling. Weave the hair in and out of the pin to create waves.

"Adir then took sections of Sienna’s hair in different widths, and curled them around his finger, pinning them with hair pins. Adir made a special point of noting “hair pins, not bobby pins!” He explained that you could do this at any angle and with different sized pieces of hair. After all of Sienna’s hair was pinned, he sprayed more Bumble and Bumble Surf spray on the ends. He then dried it slightly with a diffuser." (via welovebeauty.com)