While reading parshat Naso last week, it was easy to notice that near the end of the reading, there is a large section discussing the donations made by the 12 tribes for the dedication of the Tabernacle.
For the most part, the words in each of the 12 paragraphs (actually, 10 of the twelve) are identical except for the day of the donation and the name of the tribe leader.
Let's say a Torah needed to be repaired. Let's say that the paragraph of the 3rd day needs to be repaired (there are multiple mistakes in that paragraph). I have another passul (unusable Torah) from which I want to cutout the piece of parchment containing the whole paragraph but it's from a different day. (See this M.Y. answer regarding the fact that one may patch a Torah.) Assume that in the other passul Torah, the lettering in the paragraph that matches the day I want to replace is also passul in the same area, and a sofer declares that that other Torah can't be repaired at all because it's general parchment strength is brittle.
So, in short, when one makes a patch replacement, does he need to repatch from the same area that he is replacing, or can he take identical words from somewhere else, and just erase and change a few words that he needs to? What if he doesn't need to make any corrections afterwards, but he's just cutting out from somewhere else? Does that change the rules?