The phrase "to know a quality" means to have a deep understanding or familiarity with a specific attribute or characteristic of something.
Sentences with «to know a quality»
This gives you peace of mind knowing your quality of living will always be preserved. (himpro.ca)
We don't know the quality of the other two - thirds — the schools that never start — but we do know something about why they don't make it. (educationnext.org)
Finding a real gem in your average drugstore makes you feel savvy, like you really know quality when you see it and definitely don't care about name brands or trends. (manrepeller.com)