The Twin 6000 locks, like many high security locks, uses 2 separate shear lines. One “standard” shear line, and a sidebar. The standard shear line is fairly normal, 6 pin stacks all have to raised to the proper height to allow rotation of the plug. The twin however has a small variation, while most companies use security pins to make the picking process more difficult, ASSA uses a combination of security pins and something that has become known as “counter-milling“. The counter-milling makes picking this lock extremely hard, even without the sidebar as a second obstacle. The small groove that is cut into the plug catches the small lip on the security pins, and prevents further vertical movement. The only way around them once they are caught is to release tension and try again, very light tension must be used to get around the counter-milling. The third chamber from the front is the only chamber that doesn’t have this counter-milling, so generally while picking it is a good idea to try and set that pin last, as you don’t need to worry about the counter milling catching. The sidebar in this lock is very interesting because all the pins are the same. The actual sidebar is what holds the sidebar “code”, meaning to change the sidebar code you need to replace the sidebar, not the pins. The sidebars are generally assigned to different regions, meaning that if you buy a lock from a locksmith, all the other locks in that region will have the same sidebar code. The pins in the sidebar have 4 false gates in them, and one true gate, which is always in the middle of the pin. When they are raised to their proper heights by the bitting on the side of the key, the sidebar can retract, and providing the “regular” bitting is correct, the lock with open, else the lock will not. Since the key for the lock is very wide, the keyway is also quite large making fitting tools into the lock quite easy, however it is still a very difficult lock to pick open. Soon I will be attempting to bump open the lock, as well has trying a sidebar bypass method sometime next week. The bypass involves cutting the top bitting of and using just the bottom part to set the sidebar code, and then picking it like a regular pin-tumbler lock. I will be taking video of both methods, and posting them here in the near future.