Let me preface this with the fact that I am NOT an Assa guru, I do not claim to be a high-ranking asset on Assa technology. My exposure to Assa locks such as the Twin, Combi, and V10 are limited to a small set of locks. What you see on this document is what I have gathered based on my experience; your mileage may vary. Due to the lack of legit resources on picking this lock, this page will be an accumulation of information from different sources.
Assa, a Swedish company, is a world-class high-security lock producer under the Assa Abloy brand. Their locks have unparalleled tolerances, a tight keyway, and well designed countermilling which work together to make them very hard locks to pick. You can find these locks in scenarios such as deadbolts and padlocks.
The older models (shown in this document) have the "Gin Bottle" driver pins while the newer models have "Barrel Spool" driver pins. It is commonly stated that the older model is much more difficult to pick as the gin bottles tend to lock the plug in place when the counter milling comes in contact while the barrel spools only mildly snag.
The Twin 6000 was Assa's flagship mechanical lock design for 15 years until their release of the V-10 in 1996. The only enhancement the V-10 offered was a slightly smaller keyway. The V-10 appears to be the last mechanical advancement Assa has made to their locks. Each model after the V-10 only offered master-keying options and/or introduced electronic components (CLIQ Technology). You read that right, no mechanical advancements (anti-picking) since 1996.
It is worth noting that the CLIQ technology has already been defeated in a manner in which you can entirely bypass the electronics of it and turn the lock back into a "dumb lock" and pick it normally. source, source, source
The philosophy behind picking these locks is pretty straight forward. Of the short list of people who can pick these locks, each tend to have their own unique method of picking.
Some people prefer to pick these Counter-clockwise and only lift each pin one click as to not engage the gin bottle with the counter milling or shear line. After clicking each driver pin once, they start to attack the finger pins. Once satisfied with the finger pins they will go back to the driver pins for the final assault. Using the counter-rotation pressure from the sidebar, they will gently work the driver pins through the gin-bottle/counter-milling hell.
I personally found that the lock I had, was easier to open while picking clockwise. The sidebar and fingerpins kept the plug from rotating too far and basically denied the gin bottles from aggressively interacting with the counter milling. This made them act more like simple serrated pins. After getting each chamber to shear, the plug snapped into a shallow false set. From there I attacked the finger pins, occassionally dropping one, until the lock opened.
When the gin bottles fully interact with the counter milling, the pins cannot be lifted up and out of the milling, like a spool. The pin is deadlocked in place and you cannot lift it without manually counter-rotating the plug, which puts you in danger of dropping other pins. If you get to this scenario, the commonly recommended action is to reset the lock and start over.
While the gin bottles are difficult, defeating them is straight forward, just requires a lot of finesse. The finger pins are what take more skill in my opinion. The most important piece is the finding, or making, of a tool that will work with the finger pins. This tool needs to be able to slide under the finger pin without lifting it up (Illustration ::0 and Illustration ::1). It must also fit in the finger pin chamber while lifting the pin (Illustration ::2).
Knowing when a fingerpin is set is similar to medeco key pins. A finger pin that's tightly bound up is not in the correct gate. When the finger pin has been lifted to the correct height and set in the proper gate, the finger pin will be a little loose and you can jiggle it with your pick.
The finger pins pick like serrated pins, and have their own binding order. Lifting finger pins will cause a counter-rotation-like action on the plug. A way to tell if you're in a false gate or not is how far the plug will counter-rotate to leave the gate it's in. A false gate will be exited with a rather small counter-rotation while a true gate requires a much more significant rotation of the plug.
In my experience, when you've picked all but one finger pin to the correct gate, the lock will sink into a deep false set. This is a crucial moment and it is easy to mess up. I like to put in a second tension wrench so I can slowly counter-rotate the plug a tiny bit while maintaining upward pressure on the last finger pin until it jumps to the next gate. Be extremely careful at this moment.
Picking clockwise is a personal preference for me. Picking clockwise will typically force you to fight the finger pins last. Picking finger pins and possibly bouncing back and forth between them is a much more pleasant experience than with the gin bottle driver pins. When you drop a gin bottle, or get too many bound up in the milling, you run a great risk of dropping the other driver pins as well. When you're only picking the finger pins, dropping a finger pin isn't as big of a deal; the finger pins are the easy part by comparison.
Picking counter-clockwise typically creates a three-stage picking process and usually leaves you with picking the gin bottles last. Working with the gin bottles is no easy task. First you generally lift the driver pins until they click once, each. That should give the plug enough of a false set that the finger pins will start to bind. Defeat the finger pins and enter "stage 3" of returning to the driver pins to tackle the milling.
Deep false sets will lock the pins up hard and you will not be able to lift them. It is recommended you do NOT follow the plug into the false set while you are picking the driver pins, yet to find the sweet spot where the sidebar is on the edge of the sidebar groove. The spring pressure of the sidebar will provide some counter-rotation; this is called "Float Picking." Another method is to use two tension tools at the same time; this will allow you to control rotation in both directions. You only want to back off of tension just enough that you can force the driver pin upward and over the milling. The tolerances of this lock are amazing and you will no doubt drop other pins while setting them.
This design of pins, and the matching counter-milling, provide a terrible experience for the picker. The correct orientation of the gin bottle is for the small side (the "lid") to be facing the key. The "Lid" (Illustration ::0) has sharp edges and flat faces, the dimensions are perfectly matched with the counter-milling in the plug (Illustration ::1). The milling also has sharp edges and flat faces to eliminate any counter-rotation when picking. This provides a false feeling of having the pin set.
The finger pins (Illustration ::0) are what interact with the sidebar. The reside on the bottom-left side of the plug in their own chambers. The side of the finger pin is exposed inside of the sidebar channel of the plug (Illustration ::1). All of the grooves of the finger pin are the same depth except the true gate which is much deeper.
The gates also have sharp edges and flat faces to eliminate counter-rotation. The sidebar has flat horizontal protrusions (Illustration ::2) which interact with the gates on the finger pins. When all of the finger pins have been lifted to the proper height, all of the true gates will be lined up with the sidebar protrusions, allowing the sidebar to sink into the plug.
The sidebar is a precision-milled piece of metal that interacts with the gates of the finger pins (Illustration ::0). The flat protrusions fit inside the finger pin gates, searching for the true gate. It also has sharp edges and flat faces to eliminate counter-rotation. Unlike most locks with sidebars, the sidebar code is NOT milled into the sidebar pins. Instead, the sidebar code is milled into the sidebar. This means that all of the finger pins are identical.
The sidebar rests in the sidebar groove milled into the core which also prevents the plug from turning until all of the sidebar bittings have been satisfied (Illustration ::1). The sidebar groove is a full-length groove, so if you are shimming the lock, there is no need to satisfy the sidebar, you can just pull it out of the lock (gutting described below).
The key is another dead giveaway. The key has two adjacent rows of teeth (Illustration ::0), one row for the key pins and one shorter row for the finger pins. The key will also have the lock model stamped on it.
The tolerances in Assa locks are almost second to none. These locks are designed and manufactured with great care. You will not find any slop in these locks. You almost cannot set a pin without dropping all previously set pins, the tolerances are so fine.
Assa loves to brand their locks. The Twin is an older lock and typically doesn't have any markings on the face other than 'Assa'. The V-10 however started their love of advertising and actually has 'V-10' also stamped on the lock.
The shape of the keyway is a giveaway as well. Due to the nature of the mechanical implements of the lock, they are somewhat restricted on keyway design, so they all somewhat follow the same pattern. The bottom of the keyway has a telltail shape which allows for the adjacent row of fingerpin teeth on the key.
A quick look into the keyway will show you the first finger pin, which you can see on the youtube video preview below.
In the below video, I employ the clockwise picking method. With this particular lock, the sidebar and finger pins prevented the gin bottles from generously interacting with the counter milling. They still hung up on the milling a little, but not as much as they could. This is not believed to be common with this lock, but my sample size only consists of three Twin 6000s.
The first thing I do is apply moderate tension and lift all of the key pins until all chambers have clicked as high as they'll initially go. You may accidentally overset some, just take a mental note of which chambers have a tendency to overset and keep that in mind after you reset. Once they all start to snag a little more aggressively, I know I'm working against the counter milling. At this point I will back of of tension just a tiny, almost unmeasurable, amount. You will probably drop some pins, let this be a lesson as to how much is too much tension to let off.
With the tension backed off a little, I start forcing the pins past the counter milling. This is where the 0.015" pick starts to work against you, because under that pessure, it just deforms and bends. With some back and forth, jumping from chamber to chamber, eventually the plug will click into a deeper false set, this is the hardest part and it does take finesse and some brute force. It's easy to overset a pin.
Now it's time to work with the finger pins. At this point you can back off to a medium amount of tension on the lock. I slide my fingerpin tool into the keyway (Illustration ::0) and under each finger pin (Illustration ::1) looking for the finger pin that's bound up the hardest. Once that pin has been identified, I will lift up on the pin (Illustration ::2) while maintaining constant tension. I will lift it until it clicks once.
After it clicks, I'll give it the wiggle test. A tightly bound up finger pin is NOT in the true gate. When it's in the true gate, the finger pin will be a little loose and you can jiggle it with your pick. Once satisfied with that finger pin, I search for the next and repeat the process. In my experience, when you're down to the last finger pin, the lock will fall into an even deeper false set.
This last false set is a dangerous one. You'll have to ease up on the tension to allow you to get out of that finger pin milling. I like to use a second tension wrench to control the counter rotation, but if this core is in a padlock with a rotational spring in it, you can use that to your advantage. Once you set the last finger pin, the lock will open.
These finger pins pick like serrated pins. While it hasn't been my experience, it's theoretically possible to push a finger pin too hard and it jump over the true gate.
Gutting a twin isn't overly difficult but I felt it deserved a little writeup. The first pro-tip is to NEVER remove a plug without a key in it. The key holds the finger pins in place, they are spring loaded. If a plug is removed without a key in it, the finger pins will launch into orbit.
First, put your key into the lock. When you remove the tail piece from the plug (or whatever is holding it in the core), rotate the key to the 3 o'clock position and use a plug follower to push the plug out a little bit. You'll want to make sure the key pins are facing up (to prevent them from dropping everywhere) and that you have your finger in a position to slide on top of the sidebar (which is also spring loaded).
With everything in place, push the plug follower through the lock and ensure the key pins do not spill out and that you don't let the sidebar launch into orbit either. These springs are very small and easy to lose.
With the plug out, start dumping out your key pins. Once completed, it's time to move to the finger pins.
Turn the plug upside down and use one hand to grab the key and plug, use the index finger of the other hand to push against the key and over the first finger pin. What you're doing is sliding the key off of the finger pin while pushing your finger over the top of it at the same time. Once the key is off of it, gently lift your finger up and remove the finger pin. Repeat this process for the additional finger pins. Assembly is in the reverse order.
Since the absence of finger pins, or a sidebar, will cause the driver pins to lock up in the milling, it's my recommendation to remove the driver pins and progressive pin the finger pins first. I would start out with one finger pin, the front one. Use this to get the feel of manipulating a finger pin.
Once you have that down, next I would put the rear-most finger in pin place. This will teach you how to blindly manipulate a finger pin. Also, chances are the rear finger pin will bind second and it will let you see how a finger pin acts when it's in the true gate.
Once you have that down, I'd continue adding more finger pins, from the next rear-most pin forward. That way, the farther you progress, the easier the next one is going to be since it's closer to you.
When you're at the point you can defeat all of the finger pins in about 20 seconds or less, it's time to start adding driver pins to the mix. Remove all but the middle finger pin (this keeps the sidebar in check) and add 1 driver pin to the lock. Start learning how to work with the driver pins and counter milling.
You'll be an Assa Disassembly Master by the time you get to this point.
When you feel pretty comfortable with that, add a second driver pin, then a third, then a fourth. Once you can get it with 4 driver pins, put all of the finger pins back into the lock and work on picking an almost-complete lock.
If you can open it a few times, put the remaining driver pins in place because at this point, you're ready. The additional couple of driver pins won't add to the difficulty, only to the time it takes you to defeat the lock.