From the link I posted;
This is a tool to build a nand.bin suitable for installing on a Nintendo Wii via BootMii. It cannot build one from scratch - you must provide some data from the Wii. It needs to have a copy of the first 8 blocks of nand, a list of bad blocks, and AES & hmac keys. All of this data can be gotten from a bootmii nand dump, even if that nand is bricked.