Drilling stone buttons ~ Used a much less expensive bit, rather than a diamond bit. The Hi Power Bit (for metal, wood & plastic) was successful. Stated the larger masonry bit blew out the back and the front hole entries were also messy.
What a totally cool idea to use river rocks as towel hooks. I have used robe hooks as towels holders, but these are so much cooler. Especially if you are using river stones anywhere in you bath, ie shower walls or floors. They’d also be nice outside by a