The locks themselves are enough to keep the doors securely locked and would take a large amount of force to break open with them in the locked position.
Foxes are very clever and strong animals if they want to get to your pets then given enough time then they will. There are reports of Foxes getting into houses.
The overall protection that our hutches give is down to the size and the weight, at night your pets are well hidden away in a large secluded sleeping area and not on display.
Are hutches have a fantastic success rate regarding pets and safety and have for over 40 years been keeping pets safe.