#2 Barricades around the ringside area
Back when the metal bar barricades used to surround the ring, you never saw anyone speared or thrown through them. That was due to the fact that they weren't going to have any give way and there was no way to make them safely break.
Rings, such as those in WWE, are now surrounded by black barricades which are still incredibly sturdy, but not nearly as strong. Any metal inside of them is used more for bracing and it is quite thin, which wouldn't necessarily hurt the superstars when they are thrown into them.
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On top of that, the black pads surrounding them are made of foam which makes for even more protection when someone is being put through them quite forcefully.