AMERIMAX HOME PRODUCTS 21059 3 Inch Expandable Aluminum Gutter Strainer - Perfect for Roof Drainage & Downspout Protection

This is a very simple solution to clogged downspouts, whether they are in a gutter or (as in my case) on a flat roof. The strainer is roughly six inches tall (two to four of which will be inserted into the downspout), and is slightly tapered so that the top is wider than the bottom.The screen material is not welded together at the ends (you can see it in the picture above if you look at the back side). This allows you to "roll up" the strainer a little bit to make the bottom narrow enough to fit in the downspout's opening; when you let it go, it will expand on its own to hold it in place.Note that this will only fit in a circular opening, which is what many people have. This will not work if you have a rectangular opening, as it will leave a gap. Also note that you will still have to remove debris if it piles up around the strainer, as this will still cause water to back up, but at least you won't have a clog you'll have to roto-rooter.If you don't have some kind of anti-debris covering on your gutters, or if you have a flat rook with a simple hole for drainage, this is a low-cost, low-maintenance option I recommend.