Bobby pins come in two sizes and you have to choose the right one for the amount and type of hair that it needs to hold in place. Long grips are flat, with a "toe" on one prong, whereas standard or short grips have one wavy prong. Long bobby pins are recommended for thicker hair and they should be inserted with the "toe" on top, wiggling it through the hair up and down and then twisting it so that the "toe" is on the bottom. When securing flyouts with a standard bobby pin, the wavy prong should be against the scalp, with the bobby pin opening pointing down. Try to keep the pins closed when sliding them through the hair and let the "toe" do the work, otherwise you risk catching too much hair and give it the opportunity to slide out.