Yes it is allowed
mount -t FILE_SYSTEM DEVICE MOUNTPOINT
FILE_SYSTEM is file system you use on that media (vfat, ntfs, reiserfs, xfs, etc...)
DEVICE is a device you want to mount (like /dev/hda1 for first ide disk first partition)
MOUNTPOINT is a directory where you want to mount (like /var/backup)
Just make sure directory exists, before mounting.
Hope this helps