know (someone or something) by sight
To recognize someone or something based solely on appearance (without knowing any other information, such as a name, etc.). Even after working there for a year, there were still some co-workers I only knew by sight. I'd know the place by sight, but I don't think I could tell you how to get there.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.