It seems so simple and obvious. And I recall when just about every household had one of these somewhere in the kitchen. But now they are rather hard to find. But I still have not found a better or neater way to open cans. Mounts on the wall, the magnet catches the lid. Swings out of the way so you don’t bump into it. Even if you don’t eat much canned food, everyone opens a can now and then. It worked for your granny, it will work for you.
A cool tool is anything useful that is superior to comparable items. If you think this tool is inferior suggest a better one. You are welcome to insult a tool, but comments containing insults to individual people will be deleted. Corrections of fact are always welcomed, if stated politely. Recommendations of better tools are dearly wanted and may be elevated to the front page.