Bobby pins are made of a long narrow piece of flat metal, folded in half to press back against itself, holding hair between the two sides with a slight pressure. Some bobby pins have ridges to help secure your hair without slipping, while others have a modern sleek, flat look. Standard hair pins, on the other hand are not pressurized together, but are instead open in more of a U shape. These U shaped hair pins are most commonly used to hold a bun or updo in place. Bobby pins are generally used for pinning hair away from the face or down to the head, IE taming the flyaways. Rumor has it, they were designed to be used with the bob hair style, and aptly named after it.