what happens to sand in a sieve? what does this have to do with Montag; what camparison does he make to the sand?

In 'The Sieve and the Sand', we witness Montag's continued awareness of transition. The title of this section provides a metaphor for Montag's frustration at not being able to immediately grasp what is true in the world. Through Montag's own recollection on the train, the reader sees Montag as a young boy, desperately trying to fill a sieve with sand, an impossible task. Likewise, Montag is frustrated to find himself a sieve of sorts, unable to retain what he reads from the Bible, however feverishly he tries. On a larger scale, it becomes apparent that it is not only the words of the Bible, but truth in general that Montag finds difficult to attain. Thus, he is frustrated that he cannot fill himself or feel whole. In contrast, Millie and others like her are sieves as well, unable and unwilling to grasp information even when it is made readily available to them.

Wgat comparison does Montag make to the sand