I like to use the type of reducer that Harry Aebi made in his book. I have several different sizes to use, depending on the occasion and need. I also make my mouse guards the same way. I'll try to get a pic or two on my photobucket to share. BTW, I strongly recommend his book, The Art and Adventure of Beekeeping. It's written for beekeeping prior to TM, Varroa, SHB and CCD but is a joy to read. I especially like the low overhead ideas for beekeeping in the book. The drawings are also very period but neat.
Apparently it's out of print. I cannot find it new.http://www.amazon.com/The-Adventure-Beekeeping-Ormond-Aebi/dp/0913300381/ref=sr_1_4?s=books&ie=UTF8&qid=1332694357&sr=1-4