Phonetically, Egyptian hieroglyphs use what's called the Rebus principle. For example, in English we could write https://i.imgur.com/Rp51iOt.png (hn ate my emoji) for belief. When this symbol is used phonetically, it represents the consonants "mt" because the ancient Egyptian word for phallus used those consonants. If we wanted to write "phallus," we could write 𓂸𓏺 with the stroke afterwards to denote that we mean the symbol, not its phonetic value.
Edit: hn cut out my emoji unicode. Replaced the emoji unicode with an image link.