Change file or directory flags.

# To set the 'hidden' flag for a file:
chflags hidden <path/to/file>

# To unset the 'hidden' flag for a file:
chflags nohidden <path/to/file>

# To recursively set the 'uchg' flag for a directory:
chflags -R uchg <path/to/directory>

# To recursively unset the 'uchg' flag for a directory:
chflags -R nouchg <path/to/directory>