Rule 1 • Short Vowel → Double
When a 1-syllable word has a short vowel before a single final consonant, double the consonant before adding -ing or -ed (set → setting).
Rule 2 • Long Vowel Team → Do Not Double
When two vowels come together making a long sound (ee, ea, oi), do not double the consonant (seem → seeming, join → joined).
Rule 3 • Consonant Blends → Do Not Double
When a word ends in two consonants (-nd, -nk), the consonant is already protected, so do not double (bend → bending, thank → thanked).