The solution is a 4x4 grid of letters where each row and column match the corresponding regexes.

So the 4 letters descending from the column marked (LN|K|D)* should match the regex ^.(LN|K|D)*$ entirely. Hope that helps.

You fill the characters that would be matched by the regular expression given. So the character has to match both the row/column expressions at the position where they intersect.

Oh I gotcha. That makes more sense; I was confused since most of the expressions match more than 4 characters. Thanks!