What Are Those Hash Marks For?

I've always wondered about the hash marks that are on the touch line and goal line.  What the heck are they for?  Finally looked it up today...  They're put down to mark the 10 yd limit for defenders to approach when corner kicks are being taken.

Here's what I found about hash marks from the Laws of the Game, Chapter 1 - The Field of Play
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Marks may be made off the field of play, 9.15 m (10 yds) from the corner arc and at right angles to the goal lines and the touch lines, to ensure that defending players retreat this distance when a corner kick is being taken.
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