I purchased stanley brand one and a half inch "corner braces" which look like this http://s7d1.scene7.com/is/image/StanleyNational/reinforcementhardware-braces?$category$ you can screw them to the back wall of the incubator and then screw the other side into your fan (typically the fans will have holes on all four corners for screws but you only really need to use two) and this allows you to lower the fan as far from the top of the incubator as you like for proper air flow.