Rule 24 refers to adding endings to words ending in 'y'. When adding a vowel ending to a word that ends with a consonant and then y, change y back to an i and then add the ending. But not for words ending in the suffix 'ing' such as in playing.
For example: ba by = babies, happy = happiness
Watch the tutorial videos below to see how the Spelling Tools, Spelling Rule 24 and Reading Tools are used to spell challenging words.
Special Note:
Not all words will follow the spelling rule. These are called exceptions. If 90% or more words follow this rule then this is still a great tool to help become a proficient speller. Language experience will deal with the rest.