What’re they good for? Well, here’s our best Shmoop expert opinion: when you read a line of poetry aloud, your eyes (and therefore your voice) tend to speed on to the end of the line. Try it and see. When you read "in Just-," however, the spaces slow your eyes down. More importantly, they slow your voice down, as well. As you’re reading, you’re thinking, "Huh? I totally don’t know whether to pause for the spaces or not!" And even in that time that it takes to think that through, your voice slows oh-so-slightly. Kind of cool, huh?
This is what it would look like with 4 rows:
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That is 4 rows by 12 columns, making 48 tiles.
That means there are 2 tiles leftover.