How to
Place the magic key concentric on top of the magic cap.
Gently push the cap with the key down, before you pull both up and out.
Problems with opening
If it does not work instantly, push the cap down with the key, move the key across the cap and pull both up again. If the cap is closed for a long time, it may stick a little.
Make sure that you always have minimum one key around since it has a specific polarization. Accordingly you cannot unlock the cap with an off-the-shelf magnet.