Question : How to prevent a directory from being deleted

Have a directory from a rhel5 smb server exported to our ftp server via nfs.
NFS mount string is ~ xxx.xxx.xx.xx:/pcnet/pickup/1bb1  /home/userid/Pickup   nfs  suid,dev,noexec  0  0
There is a sub-directory structure below the FTP mount  point /home/userid/pickup/... where I need to prevent FTP users from deleteing the sub-directory.  How is this done?  Have been reading about sticky bits, but not clear on their usage and potential in this application.
Thanks in advance.

Answer : How to prevent a directory from being deleted

Do you  give ftp users full control? give them only read control. if they don't upload files to ftp link.

http://kbase.redhat.com/faq/docs/DOC-9026

here is the info about sticky bits,

http://kbase.redhat.com/faq/docs/DOC-9406