Answer:
The Sieve and the Sand" is the title of the second section of Fahrenheit 451. The title refers to Montag's childhood memory of trying to fill a sieve with sand. He's reminded of this episode as he's trying to read the Bible on the subway. While he's trying to memorize what he's reading, an announcement for toothpaste keeps derailing him. To Montag, the sand represents the knowledge that he seeks—something of material importance—and the sieve represents his mind trying to grasp and retain this knowledge.