"This extremely artful suggestion Mr. Barkis accompanied with a nudge of his elbow that gave me quite a stitch in my side. After that, he slouched over his horse in his usual manner; and made no other reference to the subject except, half an hour afterwards, taking a piece of chalk from his pocket, and writing up, inside the tilt of the cart, 'Clara Peggotty' - apparently as a private memorandum."

All the horse-drawn waggons used to have a vertical barrier in front of the driver's feet to protect against horses' hooves splashing mud on the driver. Many had on top of the upright barrier, a six or eight inch addition tilted forward at about forty five degrees, for increased protection.
Incidentally, the instrument panel of an automobile is still commonly called the "dash board" as a carry-over from the horse and buggy days.

How sweet this sentimental journey, wwh! These are things that would be lost had it not been for writers such as Dickens. Just imagining riding about in a buggy with a tilt that could double as a chalkboard for random thoughts makes me feel connected with those long gone as I jot myself notes on Post-It notes at stop lights.

I don't understand the dash board connection. The board, of course, having been made of wood--but what of the 'dash'? Why called 'dash'? Simply for speed? (Which makes me think of the dasher in the ice cream maker, but I don't suppose that's connected, too....)

A Scots lass declined to let a young Scot carry her across
the river Dee, where the ford consisted just of stone steps
spaced a stride apart.
Said he:"Is it the gleam in me ee ye're afeerd o' ?"
She replied:"Nae, t'is the tilt o' yer kilt I'm afeerd o'!"

Presumably the dashboard was to stop mud and other undesirable substances being dashed against you.

Bingley

Ah, that makes sense, Bingley. Thank you.