I use a glass drill bit for mine, works on everything I've tried so far. About an inch wide hole, they are available at Lowe's. A lot of women use them to drill those square glass bricks that they put white lights in, I'm told.

Those look cool Paula. I will look into them. My husband recently put some drainage holes in a new large pot I got, but I thought the holes were too small. I didn't know about pot drilling bits. Thanks for the info.