The bars I have are scored twice to break easier but can be broken into smaller pieces with a little more effort or scoring with a knife.
Have not tried shaving one. Really no need to . They ignite easily with a sparlite striker or ferro rod or match.
If you have not used them before, one word of caution, they burn with a clear flame and can "get you" if you're not paying attention.
They change color a bit when lit, that's when I know to move my fingers back and "not touch it again", because they do not extinguish easily.