What Is Section Stacking? Urban Myth, Apparently

This is a question for knowledgeable law professors, administrators, students, or others who are well informed.  I had never heard this term until reading the comments to the grading and scholarship posts below.  I don’t teach 1Ls, except for a specialized introduction to law and economics elective, but I had never heard of such a thing.  What is section stacking, [does it actually exist or is it an urban legend among law students – ed.], what are the reasons for doing it [if it does exist], and how widespread is the practice among law schools [if any actually do it]?

(And per Orin’s good reminder below – alleged practice, which is why I added the brackets above.  I don’t know enough about this even to be suggesting it exists. This appears to be urban legend., and I’m suddenly worried I’m spreading an urban myth meme by raising the question on the web. So just to be clear, I had never heard of such a thing until three days ago and have no reason to think it takes place.  It doesn’t take place at my school, certainly.)

Note:  I’m now sorry I ever posted on this, because it seems far-fetched that this has ever been a practice at law schools, and I think I’ve contributed to spreading a bad urban legend among law students.  I think I should leave it up, though, rather than take it down.  But I feel bad for having contributed to the spread of what seems highly likely to be Untruth & Rumor on the Internet, and at VC no less!