Linsh.rar -

7-Zip also supports solid compression using the .7z format. To make sure I'm giving you the best approach, let me know: Are you using Windows (WinRAR) or Linux (terminal) ?

Optional: Select a "Best" compression method for higher compression. Click OK to generate the solid archive. Key Considerations for Solid Archives: Linsh.rar

Adding or extracting single files from a solid archive takes much longer because the entire archive must be processed. 7-Zip also supports solid compression using the

Many small, similar files, as it treats them as a single stream to boost compression. Click OK to generate the solid archive

If you provide this info, I can tell you if you should be using the rar command-line tool or if a simple right-click in Windows will do the trick. rar - ArchWiki

Are you trying to create or turn multi-part files (.part1, .part2) into one ?

In the "General" tab, set to RAR (Solid mode only works with RAR, not ZIP). Check the box for "Create solid archive" .