Doubled Rooks on the 7th rank are very powerful and sometimes form an easy to see mating pattern. If you ever see this position in a chess game you can impress the potzers by calling a mate in 3.
PGN:
[Event "Edited position"]
[Site "-"]
[Date "2006.07.08"]
[Round "-"]
[White "-"]
[Black "-"]
[Result "1-0"]
[FEN "4rrb1/4kpp1/5N2/4P3/4BP2/8/3R4/R3K3 w Q - 0 1"]
[SetUp "1"]
1. Rad1 gxf6 2. Rd7+ Ke6 3. R1d6#
{White mates} 1-0
Franx Thanx to http://www.chessclub.com for the use of their great Java PGN utility.