You might want to consider a high quality epoxy. Your local home center would be able to give you advice on the right type. A good quality hot glue could work as well. If possible Screw and Glue would be the best bet. But chances are you don't have backing right behind the exact spots you want to put the corbels.

Thanks so much Next Level! I was hoping that I could use a glue, I will check with my Home Depot guy and find the right kind. Also thought of the same thing as far as a screw mount......probably not sturdy enough to hold. Appreciate your thoughts.