He took a small key from his pocket and slowly inserted it into the lock.
他从衣袋里掏出一把小钥匙,然后缓缓地将其插入锁孔里。
An insert is something that is inserted somewhere, especially an advertisement on a piece of paper that is placed between the pages of a book or magazine.
插入物; (尤指书刊中的) 活页广告