MIT Guide to Lock Picking – Chapter 3

In order to become good at picking locks, you will need a detailed understanding of how locks works and what happens as it is picked. This document uses two models to help you understand the behavior of locks. This chapter presents a model that highlights interactions between pin positions. Chapter 4 uses this model to explain how picking works. Chapter 9 will use this model to explain complicated mechanical defects.

The “flatland” model of a lock is shown in Figure 3.1. This is not a cross section of a real lock. It is a cross section of a very simple kind of lock. The purpose of this lock is to keep two plates of metal from sliding over each other unless the proper key is present. The lock is constructed by placing the two plates over each other and drilling holes which pass through both plates. The figure shows a two hole lock. Two pins are placed in each hole such that the gap between the pins does not line up with the gap between the plates. The bottom pin is called the key pin because it touches the key. The top pin is called the driver pin. Often the driver and key pins are just called the driver and the pin. A protrusion on the underside of the bottom plate keeps the pins from falling out, and a spring above the top plate pushes down on the driver pin.

If the key is absent, the plates cannot slide over each other because the driver pins pass through both plates. The correct key lifts the pin pairs to align the gap between the pins with the gap between the plates. See Figure 3.3. That is, the key lifts the key pin until its top reaches the lock’s sheer line. In this configuration, the plates can slide past each other.

Figure 3.3 also illustrates one of the important features of real locks. There is always a sliding allowance. That is, any parts which slide past each other must be separated by a gap. The gap between the top and bottom plates allows a range of keys to open the lock. Notice that the right key pin in Figure 3.3 is not raised as high as the left pin, yet the lock will still open.

Figure 3.1: Flatland model of a lock

Figure 3.1: Flatland model of a lock

Figure 3.2: (a) Flatland key raises pins

Figure 3.2: (a) Flatland key raises pins

Figure 3.3: (b) Proper key allows plates to slide

Figure 3.3: (b) Proper key allows plates to slide

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18 thoughts on “MIT Guide to Lock Picking – Chapter 3

  1. Pingback: » MIT Guide to Lock Picking - Table Of Contents

  2. Pingback: » MIT Guide to Lock Picking - Chapter 2: How a Key Opens a Lock

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  4. lol im only 14 and i have pick lockd like 20-25 different locks at school with paperclips you just have to do it right another good way is ( this is my way, dont care if its stupid ) use a allenkey that fits in the hols by the pin but dont press the pins all the way down press them downabout 1/4 of the way and turn the allenkey and it hould open, im only lucky most of the locks at school are wafer locks 🙂

  5. whoa i find it amazing how a lock works and tha keys to make it open and it has always fasinated me but being in my late teens i dont know much at all… so if anyone out there would like to help me out feal fre thanks nonnahs372(at)

  6. well i need to pick my basements door lock.. on it, it says “DEFIANT”.. PSHH FUCK YEA IT IS!! ive been trying to pick it with a paperclip and a small screwdriver for the past TWO NIGHTS!! my asshole father took my pool cues and my bong away from me and locked them in the dirt cellar!! AND THE FUCKERD UP THING IS THAT THE DOOR IS 3 FEET AWAY FROM MY BED!!! ive been looking at making a homemade pick but i dont have a metal grinder of some sort, so ive been reduced to paperclips.. i have it in the form of a “rake pick” and it slides in and out easily but i dont think i am pushing the back pins up to their position… if any one has any suggestions on something to grind/ cut steel tweezers (these things are TOUGH!! ive tried to file them and it dont work for SHIT!!) or if you have any other useful information, please… HELP ME!!

  7. You will have a very tough time doing this with a paperclip. The reason is that you can’t put enough upward pressure on the tumblers to get them to bind once you have put some torque on it with the screwdriver.

    When I learned to pick locks, I used a very thin butter knife that I ground into a diamond shaped pick. It worked, but it was always a struggle. If your local hardware store sells thin sheets of spring steel, I think that would be your best bet. You can then cut and grind them into the correct shape.

    For me, personally, there is really nothing quite so good as a set of “real” lock picks. I feel I could have learned the skills in less than half the time had I just ponied up the cash up front. You will also find that the correct tention wrench is worth more than its weight in gold.

    Hope this helps… Good luck defeating that lock.

  8. Hello there,
    I was cleaning out an old storage locker of mine and found some file cabinets which contain valuable information and papers which i have coincidentally been trying to find for years. The problem is that I dont have a key to these file cabinets and the combined facts that I’m under 18, am not very good with my hands, and dont have a locksmith nearby prevent me from finding a solution. I was wondering what the quickest way is to open these cabinets is (besides finding the key or breaking the cabinet) so if you have any info I would appreciate an email at Nikeman916@aol with a subject line of: File Cabinet Lock. Thanks,


  9. stoney dreadz: I think it’s time you get a new bong… This will certainly be easier than custom making picks without the aid of a grinder. So… new bong buddy… new bong…

  10. hey im 16 and i want to learn how to unlock my car door. I just hate locking myself out and i think it would be cool to be able to show off in front of my friends lol… if anyone can tell me how to unlock a car without the key then please email me….

  11. Josh,

    Am I the only one who sees the irony of submitting a comment that inquires about how to pick locks at the base of a page that discribes it in detail?

    DUDE! Read the friggin’ instructions that I have posted here! You will learn all you need to know about how to pick locks if you take the time to read these instructions and practice!

    I will warn you though that it takes a lot of prcatice. I think I cut through my first lock after taking the time to read a book and put in about 6 hours of practice. There is a reason stupid Cro-Magnon criminals need to break windows to get in. Picking locks is an elegant method of entry and it takes intelligence and dedication to learn. Only after a LOT of time and effort will you rise above the average monkey and defeat the more difficult locks. Pocking locks is impressive to your friends because it is a skill that has to be developed and honed. If everyone could do it there wouldn’t be much use for locks now would there?

  12. Please help. Are locks the same for all of the world? I am not American or Britain. I am from Czech Republic.Can I use YOUR picklocks in Czech Republic? {In our locks there are pins situated on a down side of the lock.}

  13. Hi Hanna,

    The types of locks used throwout the world are not the same, but the good news is that there are a fairly small number of lock-types in use. If I can get just a little more information on the types of locks you have there, I can certainly help you in selecting the correct type of picks to purchase.

    You say that “In our locks there are pins situated on a down side of the lock”. From the sounds of things the tumblers (pins) on your locks are inverted, meaning that they point upwards.

    Since there are at least two types of locks that situate the tumblers in this way, we need to take a look at the way the key goes into the lock to figure out exactly which type it is.

    1) Does the key slide in vertically with the jagged section of the key facing down? To illustrate, the front of the lock would look like this: (|)

    2) Does the key slide in horizontally with the flat side facing up and have dimples (partial holes) drilled into its surface? To illustrate, the front of the lock would look like this: (-)

    Hopefully these explanations are clear. If not, this link should help you figure out which type of lock you have.

  14. Thank you for your answer.I chose variation number 1 {vertically position] Please go on this webside than click on the english version.{on the right side of the page} It will be more easier for you.Than click plese on the catalogue. Go on cylinder locks. Our classical type of a lock is maybe number 4093
    You can have a look on our keys too and it’s the FAB2020 or FAB2005. I’m sorry for my bad english. I hope you’ll understand it.

  15. Hi Again Hanna,

    Please don’t worry at all about your English skills, as they seem excellent! I am very easily able to understand exactly what you mean. I am sorry that I am unable to speak your language.

    The good news is that your locks work exactly like ours do, except they are inverted. This does make them very slightly more difficult to pick, but with a little practice, you will get it in no time.

    To answer your question, you can use standard lock picks to open these locks. I do not sell them myself, but here is a link to the set that I have, and the one that I have found works best. Any standard pick set will work for you, but the steel used in these is a lot nicer than in some of the others that I have tried.

    Again, I don’t sell them myself, but if this company won’t ship to your country, I may be able to help you out getting them.

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