This article is part of our Cocktail Chatter series, where we dive into the wild, weird, and wondrous corners of history to share over a cocktail and impress your friends.

You may have noticed that coolers — especially the larger, more rugged-looking ones — have inch-long notches spanning the length of their lids. You also may have wondered why a vessel primarily used for keeping food and drinks cold comes equipped with a ruler.

No, it’s not for measuring beer cans. (A standard 12-ounce can is 4.83 inches tall, just in case you’re wondering.) And yes, that ruler can tell you whether a sandwich shop is shorting you on its foot-long sub — but that’s not what it’s there for, either. The truth: It’s for measuring freshly caught fish or crabs to see if they’re big enough to legally take home.

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If you don’t know much about fishing, there are rules set in place across the U.S. as to which ocean dwellers you can keep when you catch them and which should be thrown back into the water, and that’s largely dictated by their size. These regulations prevent the harvest of juvenile fish that have yet to reproduce and the general disruption of our aquatic ecosystems, and they vary by state. Beyond that, there are different size regulations that apply to each species of fish, as well as laws that dictate exactly how many of each fish people are allowed to catch in one day. Some species have no regulations on them, and others are prohibited from being caught at all. It’s very case-by-case, so check your state’s fishing laws before wrangling up anything you’re unsure about.

While coolers came along in the 1950s, we don’t know exactly who was the first to stick a ruler on top of them. But now, it’s fairly commonplace. And if a cooler doesn’t come equipped with one, there are plenty of brands such as SeaDek that make fish rulers with adhesive bottoms that can easily stick to cooler lids and boat decks. This way, fishermen and or plain old enthusiasts don’t have to mess around with tape measures while a fish is flopping around and dirtying up the decks of their boats.

So, if you’re ever casting a line, slap that fresh catch on top of your vessel and take stock — plain, simple, and relatively hassle-free. Or measure your sandwiches with it, whatever works.

*Image retrieved from Drobot Dean via