SEE-THRU CROSS (ZEISS) LOCK -- UNIQUE LOCK PICKING PRACTICE CHALLENGE
What's harder to pick than a single shear line? Try FOUR separate shear lines at once. The "cross lock", otherwise known as the Zeiss lock, is unique in the lock world in that its keyway is shaped like a cross (or, if you prefer, a "plus" sign). The reason it has this shape is because each arm of the cross is the front end of a separate 4-pinned stack of tumblers. In order to pick it, you'll have to get no less than 16 pin tumblers to their respective shear lines.
These cylinders are made of clear acrylic plastic (the plug itself is brass, as are the pins), giving an unobstructed view of the goings-on while you try to pick it. We supply two working keys -- which are as odd looking as the lock's keyway in that each key has a cross-shaped blade. When you insert the key, all 16 pins find their proper places allowing the plug to rotate.