Linsh.rar -

Choose "Add to archive..." from the context menu. Configure Solid Option:

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

Adding or extracting single files from a solid archive takes much longer because the entire archive must be processed. Choose "Add to archive

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