Oh, sorry, I forgot. The command is more like this:
mount -t cramfs -o loop /tmp/cram0 /tmp/crammountpoint
The -o loop tells the mount command that this is a file, not a physical device, that's what it meant by "Block Device Required". Also, I don't know what you're using it for, but it's more canonical to put mountpoints under /mnt or /media. It's not the only right way, just the canonical, "normal" way.