Can you use a 1x6 across rafters to hold ceiling fan?

Yes, you can use a 1x6 board across rafters to provide support for a ceiling fan, but it must be securely fastened to the rafters to ensure stability. Additionally, it's important to ensure that the board can handle the weight and vibrations of the fan. Ideally, a ceiling fan should be mounted on a dedicated fan-rated box or bracket designed to support such loads for safety and performance. Always follow local building codes and manufacturer instructions for installation.