You can vape a cartomizer by itself, refilling it as needed. That's "unpunched."
If you want to use a slip-on tank over it to increase the capacity, you need holes or a slot for juice to get from the tank into the cartomizer's filler. You can use a punch to punch holes in the cartomizer, but this invariably distorts the roundness, which is hard on the tank o-rings and can cause leaking. You can use a cutting wheel on a Dremel to cut a slot, but then you have metal dust everywhere and potentially jagged edges, also hard on the o-rings.
You can buy punched cartomizers that have been manually punched, but usually not perfectly round either.
The best solution is to buy laser "punched" or laser "slotted" with smooth clean holes or slots, which aren't much more expensive when you consider the life they add to your tank o-rings.