Uptowner allows a user with administrative privileges to temporarily become the owner of a file and its enclosing folder. It temporarily promotes you "up to owner", hence the name Uptowner.
Sometimes I look at a root owned read-only file when logged in with administrative privileges, then decide I'd like to make a change. That's when Uptowner comes in handy. Start by finding a file (a text file is simplest) in a window that has the "pencil with a line through it" icon. A fairly safe file to play with might be one of the .log files in /private/var/log. To go there, just choose "Go to Folder..." from the Go menu and type in "/private/var/log". Drag a file onto the TextEdit application's icon to open it. Make a change such as typing a space then pressing the delete key once and try to save it. If you can't, which is likely, you can use Uptowner. While the file is still open in TextEdit, drag the file's icon to the Uptowner application icon or its Dock icon if it's already running. Enter your administrative password (you must be logged in with administrative privileges to use Uptowner). Click "Become temporary owner" then OK the warning message if you're brave enough, and go back to TextEdit. You should now be able to change and save the file. Uptowner will wait for you to tell it that you're ready for the original ownership to be restored for the item you selected. Go back to Uptowner and click OK again and everything is set back the way it was and you'll no longer be able to change and save the file in TextEdit, unless you use Uptowner again.
Another Warning! Do not attempt to change ownership of items that you can't read when logged in as administrator. Please use Uptowner with great caution.