 on a good solid base, then it's good. But I like to be able to fill the cracks and be able to use a power washer on it. So, Leslie, I'm thinking that with flagstone being an irregular surface like that, I've seen people try to fill these cracks and spaces between with mortar, but it never works out because it's not designed to be that strong. Well, no, and I always feel like when you have mortar in between flagstone with the freeze and thaw cycle, it just cracks out.