How the heck do you even climb this. I don't see any places to grab hold? There are gaps between the cubes I guess but those seem awfully smooth and slippery...
The metal cage that the plastic cubes sit in. On the corners where they bend, there's room to get fingers wrapped around. They're also rectangular and pretty chunky. It's not super comfortable, but it's secure.
Also, fun fact: they are literally held together with large metal zip ties.