Why does the clerk go down the slide twenty times in "A Christmas Carol"?

Question

In "A Christmas Carol", when the clerk gets off work, he leaves, goes down a slide twenty times, and then runs home:

The clerk promised that he would, and Scrooge walked out with a growl. The office was closed in a twinkling, and the clerk, with the long ends of his white comforter dangling below his waist (for he boasted no great-coat), went down a slide, at the end of a lane of boys, twenty times, in honour of its being Christmas Eve, and then ran home as hard as he could pelt to play at blindman's buff.

Why does the clerk go down the slide twenty times? The story says "in honor of its being Christmas Eve", but I'm failing to grasp the connection. I'm not very familiar with Christmas customs, but I've never heard of going down a slide being one of them.
If this was the clerk going down the slide with his kids, that I'd understand, but this is apparently him going down the slide before getting home and seeing his family, as an adult, waiting in line for the slide with a bunch of young boys. This strikes me as a bit odd.

Why does the clerk do this? Why is this included in the story?

Answer 1

This is the kind of slide that kids make by sliding on an icy pavement until it is smooth and slick.

A smooth surface, esp. of ice, for sliding on, or formed by being slid on; a slippery place. OED

Clerks in Scrooge’s establishment didn’t get much cheer in their lives and few holidays to enjoy their own time, so having enjoyed the exhilaration of the boys’ slide and being free of the need to behave in a meek and disciplined manner for his boss, he celebrates the holiday with the childlike indulgence of sliding.

In terms of the story this makes clear to the reader how much pleasure the clerk, Bob Cratchit, takes in his temporary release from Scrooge’s control.

Edit: to be clear, there is no particular significance I’m aware of to the number twenty. Dickens just wants us to understand that he didn’t just slide a couple of times as he passed, but that he really spent some time enjoying a childlike pleasure.