What are the opposite words for unfasten?

The antonyms for the word "unfasten" are numerous and varied depending on the context in which it is being used. The most common antonyms for "unfasten" include words such as "fasten," which implies that the object or item is securely attached or connected. Another antonym is "lock," which refers to the act of securing a device or object and making it immovable. "Clasp" is another antonym that typically refers to objects that are held together by a fastener or closure. Other antonyms for "unfasten" include "attach," "link," "tie," and "connect," all of which denote actions taken to keep things together.