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I find the easiest way is to use patterns - create a new document (transparent background) 2x2px - fill the top left and bottom right pixels with black (or whatever colour you want). Then select all (CTRL+A) and go to edit > define pattern.
Now if you select the single row/column marquee tool and make your line just fill it with the pattern you just made.
To make the dots more spaced just adjust the size of the document you use to make your pattern
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