When adding ing, ed, er or est to a base word with a vowel diagraph or ending in a consonant diagraph, JUST ADD the suffix. When adding ing, ed, er or est to a base word ending in one vowel/one consonant, DOUBLE the final consonant before adding the suffix. 1. Tap tool to type the correct spelling when adding each suffix. 2. Move each word to the correct column. 3. Check each word with the rules written above and on the activity. 4. Tap to send it to your teacher.