"Locking" directories is not something anyone should do. However, if you want to protect some files or directories with a password, you should encrypt them. I suggest looking up GPG and LUKS (you can make encrypted disk images or partitions and mount them to folders).
Very true that. Most of the time users will tell you they need a thing and in fact it is completely different thing they really desire, they just did not have the right words for it or did not think it throughly enough.
That's why we have grooming sessions for