In Hittite cuneiform, every glyph with a phonetic meaning is either V (a vowel), CV (a consonant followed by a vowel), VC, or CVC. As a result, there's no way to represent three consonants in a row without adding an extra "empty" vowel: a word like walhteni has to be written wa-al-ah-te-ni.
When I'm looking at an inscription, is there any reliable or algorithmic way to know if a vowel is "empty" or not? In my limited experience, I haven't seen very many VC-VC sequences with both vowels pronounced—but I don't have a very good sample size to extrapolate from.