Antonyms for the phrase "rap knuckles" include words and phrases such as "gentle touch", "caress", "stroke", "soothe", and "tender massage". While "rap knuckles" suggests a rough and forceful action, these antonyms indicate gentle and tender actions. These words and phrases are commonly used in the context of physical touch or massage, and convey a sense of comfort, relaxation, and healing. While "rap knuckles" may be used to communicate a sense of authority or punishment, the antonyms suggest a much more caring and nurturing approach.