5 Stars: Toplus Baby Safety Magnetic Cabinet Locks - No Tools Or Screws Needed (6 Locks + 2 Keys)
These cabinet locks stick on with 3M tape so there is no need to damage cabinets with screws.
They way these work is one piece goes inside the cabinet with a hook that keeps the cabinet closed. You place the "key" (a round knob looking piece) on the outside of the cabinet over the hook and the hook releases.
Since the key is magnetic, we keep it on the fridge so we don't have to worry about losing it. Since these stick on with 3M tape, they are easily removed, too. The plastic feels really sturdy and like it will last a while. The package also comes with extra 3M tape should you need it. There is also a "switch" to keep the cabinet unlocked if you desire.