Taxy, I wondered the same thing. Which means I ran off to google because I love knowing how things work! I found a place that said the safe-cut can openers essentially break the seal between the can and the lid. It did not say how it did this but, if you look at Andy's video, stop at 3.59. You can see the lid is popped off from the rest of the can leaving two pieces with no rough edges. It makes sense to me that the can would have to be smooth before being capped with the lid in manufacturing. The picture seems to support that as well as the lid being able to replace as "temporary storage." As for how the can opener breaks the seal, I am saying, "Kitchen magic."