Everything I Know About Mul-T-Lock MT5/MT5+ By: MMDeveloper;
Last Updated: 2017/07/24

Prologue

Mul-T-Lock (hereby known as "MTL") is a maker of world-class dimple locks under the Assa Abloy umbrella. Their flagship products, at the time of the creation of this document, are the MT5 and MT5+ dimple locks. These carry a well known high-security reputation and there are very few people that can open these with ease.

What Is An MT5/MT5+

The MT5 is a high-security dimple lock that utilizes Pin-In-Pin technology, along with an interactive alpha spring at the tip of the key (Illustration ::0). This alpha spring adds a key control feature in that photographing the key gives you no information on how high the alpha spring pin needs to be lifted. Each of the keypin chambers in the plug are countermilled (Illustration ::1). Each of the inner driver pins are counter milled and they snag on the outer key pins which are also counter milled (Illustration ::2).

The MT5+ adds an additional mechanism, a sidebar (Illustration ::3). This sidebar introduces sidebar pins that are 90 degrees perpendicular to the keypins. These sidebar pins have tiny fingers that protrude into the edge of the keyway, they are also full of false gates (Illustration ::4). These fingers interact with a laser-track that is milled into the key. This track pulls the sidebar pins into the lock and the right position for the true gates to line up with the sidebar.

Illustration ::0
Alpha Spring on Key
Illustration ::1
Countermilled plug
Illustration ::2
Countermilled pins
Illustration ::3
MT5+ Sidebar
Illustration ::4
Sidebar Pin

Picking Philosophy

Picking these locks, on paper, is pretty straight forward. Generally, when picking in a clockwise direction, you will want to make sure you slide all of the sidebar pins to the side of the key way if you're picking an MT5+. If you are picking a regular MT5, skip this step. Next, you want to check the alpha spring. Typically this is the first binding pin. These are always standard pins and will give a stout click. Next, you go after the outer key pins. Once the outer key pins have been set, it's time to start going after the inner key pins. This is where it starts getting tricky.

Using a delicate touch, start setting the inner key pins. If you're careful, you won't allow the counter milled parts to snag on one another. Once the pins are satisfied, if it's an MT5 the lock will open.. If it's an MT5+, the sidebar pins will then be bound up tight. Utilizing a small tool, manipulate the sidebar pins to the correct positions and the lock will open.

Trademark Security Mechanisms

Pin-In-Pin

The pin-in-pin feature is the most prominent amongst Mul-T-Lock devices. As stated before, it consists with an outer pin that has a hole drilled through the center where an inner pin resides (Illustration ::0). It is fairly common for these pins to be countermilled so they lock together if you tension the lock too hard.

Illustration ::0
Pin In Pin

Counter Milling

This is a feature in which a pin is cut in a manner that will interact with matching cuts in either a chamber (Illustration ::0) or another pin (Illustration ::1). This causes the parts to hook together or seize up the core, adding a great deal of pick resistance. Usually countermilling involves under-cutting a chamber that also contains a security pin. The sharp edges of the security pin will snag on this undercut. In the case of Mul-T-Lock, they will both undercut chambers AND make the inner/outer pins snag into each other through countermilling.

Illustration ::0
Countermilled Chamber
Illustration ::1
Countermilled Pin

Sidebar

The sidebar, applicable to the MT5+, is no different than any other typical sidebar in any other lock. It uses tiny fingers of sorts to interact with true/false gates in sidebar pins (Illustration ::0). In the case of the MT5+, the sidebar pins are separate from the inner/outer pins. These sidebar pins move in a lateral, sideways, direction, 90 degrees from the upward direction of the key pins (parallel with the shape of the keyway) (Illustration ::1). The sidebar pins have a small finger protruding from one side that interact with a laser track cut into the edge of the key (Illustration ::2). This track will pull the sidebar pins toward the key pins, to line up the true gate of each sidebar pin with the sidebar.

Illustration ::0
Sidebar
Illustration ::1
Sidebar Pins Location
Illustration ::2
Sidebar Pin

MT5

Security Mechanisms

  • Pin-In-Pin
  • Countermilling
  • Interactive Alpha Spring
  • Great tolerances

Tools Used

  • Cheap Z-Bar tension wrench
  • Custom flag for key pins
    • This is a standard flag that I've filed down short/small enough that it will fit inside an outer key pin. This is so I can lift inner key pins higher than the bottom of the outer key pin, if need be. Think of an American flag that I've filed down starting from the top until all of the blue was gone.
  • Small half diamond

Picking

Picking these is pretty straight forward, on paper. Typically what I do is first I'll apply moderate tension to the lock and go after the alpha spring. The alpha spring almost always binds first. The alpha spring is the 6th pin in the chamber, but it is slightly off-center. It's a very small pin, almost flush with the top of the keyway, about 1/16" to the left of the outer key pins. This is what I use the half diamond for as it's a very small pick and is pointy enough to fit into the small hole that the alpha spring keypin sits.

After the alpha spring clicks into place, I bring out my custom filed flag pick. Maintaining medium tension, I go down the pin stack with my pick angled upward. The pick is pushed until it hits the side of an outer key pin. At this point I carefully angle the pick back down flat until it slides under the edge of the key pin. With the pick barely under the edge, I lift the outer key pin only to check if it's binding. Once I find the binding outer key pin (the outer pins usually always bind first), I lift it until it clicks and repeat the above steps to the next outer pin. It's very important to make sure you are only lifting the outer pin, and not accidentally lifting the inner pin with it (hence the small flag).

After the last outer pin is set, the lock should fall into somewhat of a false set. Repeat the above steps except you are targeting the inner key pins now. Once you've lifted each of the key pins to a click, the lock will either open, else you're stuck on counter milling. From here I will ease up on the tension a little and start poking around randomly on both inner and outer key pins until you find the one that's stuck. At this point the lock should be in a pretty deep false set so don't be scared to push up on the pins with a little force to overcome countermilling.

MT5+

Security Mechanisms

  • Pin-In-Pin
  • Countermilling
  • Interactive Alpha Spring
  • Sidebar
  • Separate sidebar pins with true/false gates
  • Great tolerances

Tools Used

  • Cheap Z-Bar tension wrench
  • Custom flag for key pins
    • This is a standard flag that I've filed down short/small enough that it will fit inside an outer key pin. This is so I can lift inner key pins higher than the bottom of the outer key pin, if need be. Think of an American flag that I've filed down starting from the top until all of the blue was gone.
  • Custom flag for sidebar pins
    • This is a standard flag that I've filed down both short enough, and shallow enough, that it will fit inside the chamber of a sidebar pin, and I can rotate the pick without it binding up in the keyway.
  • Small half diamond

Picking

Picking these is pretty straight forward, on paper. Typically what I do is first I'll apply moderate tension to the lock and go after the alpha spring. The alpha spring almost always binds first. The alpha spring is the 6th pin in the chamber, but it is slightly off-center. It's a very small pin, almost flush with the top of the keyway, about 1/16" to the left of the outer key pins. This is what I use the half diamond for as it's a very small pick and is pointy enough to fit into the small hole that the alpha spring keypin sits.

After the alpha spring clicks into place, I bring out my custom filed flag pick. Maintaining medium tension, I go down the pin stack with my pick angled upward. The pick is pushed until it hits the side of an outer key pin. At this point I carefully angle the pick back down flat until it slides under the edge of the key pin. With the pick barely under the edge, I lift the outer key pin only to check if it's binding. Once I find the binding outer key pin (the outer pins usually always bind first), I lift it until it clicks and repeat the above steps to the next outer pin. It's very important to make sure you are only lifting the outer pin, and not accidentally lifting the inner pin with it (hence the small flag).

After the last outer pin is set, the sidebar should be bound up pretty good. Manipulating the sidebar pins, IMO, can be difficult to get right. I've found that you have to really let up on the tension in order to move the sidebar pins. Letting up on the tension a little, I'll use my custom sidebar flag to check each sidebar pin for how tight it's bound up under tension. When a pin is in a false gate, it will be bound up really right. When in the true gate, it will wiggle a little bit. Using the flag to move the sidebar pins (one at a time) one click at a time and performing the wiggle test you should eventually get the sidebar pins set.

It's not uncommon to accidentally drop an inner pin while doing this so you may need to manipulate the inner pins again.


Learning How To Pick An MT5/MT5+

Introductory Locks

An introduction to dimple locks would be a brand called "Kenaurd" dimple locks on e-Bay. These are knockoff Mul-T-Locks that are extremely eash to pick open. If you feel you are beyond that, you can explore older Mul-T-Locks, such as the Classic, Junior, and 7x7.

Progressive Pinning

In my opinion, this is the best way to learn how to pick a high-security lock. Personally I'll try and pick the entire lock at first, just to see where I get hung up so I might know where to focus on more.

When progressively pinning an MT5/MT5+, first I'll remove the sidebar and all of the sidebar pins (if applicable). I will then remove all but the first inner/outer key/driver pin sets. I'll then practice opening a 2-chamber MT5 lock. After I have that down I'll add the third chamber and pick some more. Then a fourth, a fifth, and finally the alpha spring is added. If you have a good working skillset for dimple locks, you should be able to progress up to a 5 or 6 pin MT5 within the hour. If you're starting fresh, maybe a few cumulative hours.

In the case of the MT5+, and I've defeated the key/driver pins, I'll remove all pins and put the sidebar back in, with 2 sidebar pins. I'll then practice manipulating the sidebar pins until I feel pretty good with 2 sidebar pins. After that I'll add two more and work on that until I feel good. After that I'll add the remaining sidebar pins until I can regularly defeat the sidebar.

Once the sidebar is defeated, I'll re-pin the first 2 key/driver pin chambers so I have to defeat two pin chambers plus the sidebar. Once I have that down I'll re-pin the rest of the chambers. At this point, you've defeated all of the security features separately and now it's time to put all you've learned to the final test with a fully assembled MT5+.