The problem with the tins that have ring/tabs for opening them is that inevitably, at some point, they break
I use my "can opener" all the time but not for opening tins. I use the bottle opener part on it to remove the lids from the foods I can/bottle. I can't imagine someone not knowing what a tin opener is
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*Unless you're talking about the really old school type which is essentially just a blade. I've never used one that doesn't have rolling gears, so I'd be at a complete loss as to how to actually use one of those.