Anchor pins are used by florists to hold florist foam in place in the bottom of containers, attach items such as votive candles to extension rods and candles to foam.
You put a small piece of florist clay on the underside of the pin and then push it firmly onto the bottom of the container.
They work well on the bottom of pillar or votive candles as well.
Simply glue or attach with florist clay and put the anchored candle into the top of the foam.
I sell the clay floral adhesive in my online store as well.