The layman term for drain cover (grate) is manhole cover. Say "manhole cover" and pictures of patio drain grate /heros using the underground sewage system popping out of manhole cover in Hollywood films appear.
Historically since that time Man invented the sewage system since the Roman Times to drain water and urban waste away for sanitation purposes, manhole covers (drain covers or grates as we prefer to call them) have already been invented out of the necessity to avoid people from falling into underground sewage and also to prevent large objects from entering the drains which cause choking which eventually may cause flooding.
Fast forward to the present day, the sewage system is still utilised under all cities all over the world. Instead of the crude stone manhole covers the Romans use in the ancient days, we now have special steel reinforced stone gratings that provide the thousand year old function of covering the inlets of our sewage system.
A lot more than a cover, check out Jonite's range of drain covers (drain gratings) here: https://www.jonite.us/products/creative-grates
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