The words know-how, no-how sound the same but have different meanings and spellings. Why do know-how, no-how sound the same even though they are completely different words?
The answer is simple: know-how, no-how are homophones of the English language.
The knowledge and skill required to do something correctly. See Synonyms at art1.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition, and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").