Recombining split files
Data may be transferred in split files, which will commonly have the extension .bin or simply .001, .002, .003, etc.. These files can be re-combined into the .RAR format, a common archive format similar to .zip. You can use a command in DOS to recombine these binary files into a single .RAR file that can be opened.
copy /b splitfile1.bin + spiltfile2.bin "2019LItSupport.rar"
Two files, 'splitfile1.bin' and 'splitfile2.bin' from separate discs or downloads, become a single rar file that can be opened in WinRAR or 7-zip.
7-zip also contains a utility to re-combine split files but WinRAR does not.