1 Monty: Anyway, I don't know where Dr Smith is. We parted on decidedly unfriendly terms a few weeks ago.
2 Alice: Oh, that's a shame. I was looking for someone who can decipher Ancient Egyptian hieroglyphs.
3 Monty: I can read Ancient Egyptian hieroglyphs!
4 Alice: Yes, but can you decipher them?

People sometimes call these Ancient Egyptian writing characters hieroglyphics, but technically the noun form of the word is hieroglyph, and hieroglyphic is an adjective, used in compounds such as "hieroglyphic characters" or "hieroglyphic writing".

Of course, English being what it is, you can probably get away with calling the characters "hieroglyphics" and you'll be fine unless you run across an archaeology or grammar nerd.