FLOSS RULES provide guidelines for doubling consonant letters when adding suffixes to words ending in short vowels. The rules are that one-syllable words ending in f, l, or s get their final consonant doubled if the vowel is short and preceded by one consonant. Examples of words following this pattern include bell, chill, and pass. There are some common exceptions like if, gas, and bus that do not follow this doubling pattern. Final s sounds that make a /z/ sound are also never doubled, such as in words like his and was.