Anvi Folder Locker is a free tool which allows you to limit access to certain folders.
To conceal a folder from others, for example, you would right-click it and select "Lock with Anvi Folder Locker". Set or enter your master password (to make sure no-one else can remove the protection later), set your protection type to "Hide", and that's it: the folder will no longer be visible in Explorer or at the command line.
It's also possible to password-protect a folder, or set it to read-only. Your protection type can be changed from the Anvi Folder Locker console, or removed entirely in a couple of clicks.
We experienced one technical problem with the program, as it displayed an "Ordinal Not Found" error message on every launch. But this didn't affect functionality, and we suspect it's an issue specific to our test system rather than a general bug.
There were a couple of other small issues. If you remove protection from a folder then it doesn't become visible in any open Explorer folders right away, even if you refresh (you need to close and reopen Explorer). And if you right-click a folder while the Anvi Folder Locker console is open, the "Lock with..." menu entry doesn't appear.
Despite that, Anvi Folder Locker's ability to hide, password-protect or make a folder read-only is relatively unusual, and if you need that kind of security then we'd give it a try.
Version 1.2 changes:
1 Add new language-Chinese
2 Improved and allow automatic updating for this program.
It has a few workflow issues, but Anvi Folder Locker Free's range of protection methods helps it stand out from the crowd. It's not just about hiding a folder, or password-protecting it, or make it read-only - you get them all. Worth a look.