The words racking, wracking sound the same but have different meanings and spellings. Why do racking, wracking sound the same even though they are completely different words?
The answer is simple: racking, wracking are homophones of the English language.
A method of asphalt shingle application, whereby shingle courses are applied vertically, up the roof rather than laterally across and up.
spun yarn used in racking ropes
Present participle of rack.
Present participle of wrack.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.