"A Strip Of Black Dots That Runs Along The Outside Edge Of Your Windshield"
"That black strip is called a "frit" and it essentially has two purposes. It provides an etched surface for the adhesive to adhere to, which bonds the glass to the frame. And on the outside of the glass, it protects the adhesive from ultraviolet light and covers any unsightly adhesive. The dots are there just to make it look nice."
https://www.amazon.com/Panef-Corp-Powdered-Graphite-Lubricant/dp/B0016GZQ60
Now I don't use hairpins but I would think the side WITHOUT the sharp pointed end would be better against your scalp?