First it was a lamp oil bottle. The cap resisted, I ended up cutting the bottle opened and poured the oil in a recycled, normal-capped water bottle.
Then it was a jar of medicine. In our effort to open it, we actually split open the top part of the drop-controlling thingy, which means we still can't open it, but the liquid will pour out of the bottle. Great child-proofing.
Then it was a bottle of insecticid treatment. Neither of us could open it. We checked our ID: we're clearly adults. Why is it we can't open child-proof bottles?
In a fit of revolt against this adult-proof world, I took the insecticid bottle back to the shop. The lady at the counter called in another girl saying I had problems with a child-proof cap (why didn't she try it herself? It's a conspiracy I tell you) and the other girl, a small-ish, weak-looking woman, said "you need to press it down hard you know". Well yes we tried that. So she pressed it down and turned, and it opened. Imagine that.
My theory is that they have one, specially child-proof-cap-opening trained staff member, who's chosen for a small-ish, weak-looking, female qualities, just to humiliate those of us who are male, strong-looking, and child-proof-cap impaired.