Use WinRAR: Right-click the files > "Add to archive..." > Select "RAR" as the archive format.
Open the file in WinRAR, click the "Repair" button in the toolbar. kaktotio.rar
If the file is or if you are looking to split a large file into smaller pieces , let me know—I can provide steps for that too! Use WinRAR: Right-click the files > "Add to archive
If you want to compress files into a RAR archive: kaktotio.rar
You can find the file format specs for developers on Kaitai Struct .