No really, they have a mark on them and break off clean if you pull them the right way. If you don't it will be a mess. Trust me, I leaned the hard way.
I've never filed an amp. Or used any tool to snap them. And Pillar - da fuq is a bicep pen?
Like Cecil said - some amps do have a dot, but not all.
Just pinch the top and bottom with opposite hands close to the spot where it breaks, pinch it tight, and snap it like you're tearing a band-aid.
There should be a dot or some sort of mark on the neck, that's the scored point. You want to pull the top back away from the point.
https://www.google.com/webhp?source...=2&ie=UTF-8#q=how to break open glass ampoule
If you're a puss you can put an empty alcohol wipe wrapper over it or use a syringe barrel to break it. Either way, look for the dot, they're only designed to break off in one direction.
http://3.bp.blogspot.com/_0e2tmUyBU...AAJQ/hnLVBw0Fhb8/s320/water_glass_ampoule.gif
http://www.scielo.br/img/revistas/rba/v61n4/en_a13fig03.jpg
You can use an empty 30.06 shell or 44mag shell to put over the top and crack open. Works great. Just find what shell fits best and you're set. Hope that helps.
!S!