WinRAR has a feature that allows archive creators to lock an .rar archive or SFX executable (.exe) in order to protect the RAR packed or packaged archive from modification and change. When the WinRAR archive locked, everybody cannot change the content in the archive, be it files, folders, comments, SFX options and modules. Unlock doesn’t open password protected archive. It simply allow the archive’s content to be modify.
However, the protection of RAR archive or SFX executable is not foolproof, as it can be easily unlocked, by just patching a few bytes. WinRAR Unlock is a small utility that does exactly that to unlock WinRAR archive (including SFX), effectively allowing anybody to modify, edit or change the content of archive freely.