An uithangbord is a sign hanging from the façade of a building. Many businesses had one. It served as advertising and as a form of address: people often referred to a house by the sign that hung from it.
In old court records, you can sometimes find references to these signs, for example in phases like “. . . sells his inn at the Achterstraat, where the Red Lion hangs from.” The photo below shows an example of such a sign, hanging from an inn that dates to 1677.