noun
Refers to the # symbol. In Japanese contexts, it is often called シャープ (sharp) in music or 井桁 (いげた) for the shape, but 番号記号 is a formal term for the symbol used in numbering or as a hash/pound sign.
電話番号の前に番号記号を入力してください。
Please enter the number sign before the phone number.
この書類では、番号記号は番号を示すために使われています。
In this document, the number sign is used to indicate a number.