Sitefinity Shell is a backend command-line tool for the Sitefinity CMS to help improve some administrative tasks like:

• Find pages with certain characteristics - those with the Require SSL field, a certain template or cache setting
• Modify some pages for a particular subtree: change the Require SSL flag, the cache settings, or trim older versions
• Republish some parts of a site - a page subtree, only the pages with a particular, all the images... or all the content of your site (including Dynamic Modules)
• Examine the error logs from Sitefinity even if the process holds a lock on them
• Determine what errors are the most common, or what URLs generate the most errors
• Examine the SiteSync logs, including a full comparison between what the Source and the Destination site logs

Check here

Just copy the files from the bin folder to Sitefinity's bin folder. Sitefinity will automatically add a "Shell" page in the Administration menu.

To rebuild for another Sitefinity version:

• Copy the SitefinityShell folder to Sitefinity's "Projects" folder. It should be on the same level as the _EmptyProject folder.
• Open SitefinityShell/SitefinityShell.csproj in Visual Studio
• Rebuild the project

To uninstall:

• Delete the SitefinityShell.* files
• Go to Administration / Backend Pages to delete the Shell page