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The Tension Wrench - Everything You Need to Know About the World's Most Popular Turning Tool

Lock Picking Tools - The Tension Wrench
Last Updated on January 31, 2021
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The tension wrench at first glance may seem like a simple tool. You just cram one end into the keyway and apply force to the other end, right?


The truth is, if we take a step back and examine our tension wrenches, we might notice some characteristics that spark some interesting questions. Such as:

  • Why do some tension wrenches have a twist and others don't?
  • Why do some have two ends with two different lengths?
  • What is the purpose of these two lengths; when do I use the short end and when do I use the long end? Does it matter?
  • Is the standard tension wrench only for beginners and when should I abandon it for a top of the keyway turning tool?

There are so many questions that surround this itty-bitty bent piece of metal and so many different qualities that go ignored.

However, by truly understanding these qualities you can better utilize this tool to its and your full potential.

So let’s take a deep dive into the characteristics of the world's most popular turning tool – the tension wrench!

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The Tension Wrench

The tension wrench is a very simple creature that is typically nothing more than a flat strip of steel that has been bent to a 90-degree angle and consists of both a short and long end.

The shorter end is typically long enough to enter at least halfway into the length of the keyway. This is the section of our wrench that will act similarly to the blade of the key and turn the plug.

The longer end will act as a lever that we pickers will use to apply force to the plug.

Introduction to the tension wrench - how to use the tension wrench

The tension wrench is designed and intended to be used at the bottom of the keyway (BOK) and is the ideal tool for picking a lock in your hand.

It is by far the most common turning tool found today and is the bread and butter of any good lock picking set!

There are tons of variations of the tension wrench from its style, size, and length. We’ll cover the purpose of each variation later in this guide, but first, let's take a gander at what makes these turning tools so popular and what drawbacks you might encounter while using them.

Benefits of the Tension Wrench

1. They Are Cheap

The tension wrench is nothing more than a small strip of spring steel that has a few slight bends applied to it. It truly is a simple design constructed from a simple material, which makes it not only easy for manufacturers to make, but also very cheap!

You can typically snag a good variety of tension wrenches for around $10 – like the Peterson 6 Piece Tension Tool Set!

2. Lock in Hand Comfort

How to grip a tension wrenchWhen used in the bottom of the keyway, the tension wrench sticks out at an angle that is very comfortable to apply force to when you are picking a lock in your hand.

For this reason – along with being extremely cheap – the tension wrench is an excellent beginner tool as most individuals learning how to pick a lock typically begin with padlocks that can easily be tensioned from the bottom of the keyway.

However, note that this benefit can quickly turn into a nightmarish drawback if you are left-handed.

3. Provides Leverage for Your Pick

When picking a lock, we sometimes have to leverage our pick off the bottom of the keyway or even some lower warding in order to fully lift a pin to a set.

However, some keyways can be very large and have a huge gap between the area in which you can leverage your pick and the pins. This massive gap can make leveraging your pick and reaching the pins very difficult.

Using Tension Wrench to Help Leverage Pick

Using a tension wrench at the bottom of the keyway can provide a platform that gives you a higher point of leverage and helps reduce the distance between your pick and the pins. It also gives you a smooth base to slide your pick on.

4. No Room Up Top

Some locks have extremely tight or paracentric keyways (curved) that make it nearly impossible to fit any sort of tensioning tool at the top of the keyway.

As a result, we are typically left tensioning from the bottom of the keyway using our tension wrenches. So don't be fooled into thinking tension wrenches are just for beginner locks, they have their place throughout the entire spectrum of lock picking!

Drawbacks of the Tension Wrench

As we can see there are some great reasons to use a tension wrench as your go-to turning tool, but sadly nothing is perfect. Let's look at some of the drawbacks of the mighty tension wrench!

1. Can Take Up a Lot of Room

Perhaps the greatest drawback and the primary reason many pickers transition to a top of the keyway turning tool – such as a prybar – is because the tension wrench can take up a TON of useful room in the keyway.

This gives us as pickers less room to maneuver and leverage our picks and can make picking some locks very difficult, if not impossible.

2. Binding the Core

The second greatest drawback of the tension wrench is that because you are turning the keyway from the edge, the force on the wrench can easily be transmitted directly into the body of the lock.

This results in binding the core – otherwise said, the plug won't rotate. You can also bind the core by using a tension wrench that is too small for the lock.

In addition, there are some locks that are designed to bind if tensioned from the bottom of the keyway!

3. False Feedback

Because tension wrenches are used at the bottom of the keyway, they typically rub against the inside of the keyway.

Not only can this cause excess friction, but if there are any nicks, dents, or slag on your wrench or on the inside of the keyway, you may encounter false feedback or even bind your turning tool.

4. Too Much Rubbing

Lastly, because your tool is rubbing against the bottom of the keyway, you can easily erode away sections and create a rut that your tension wrench will get stuck in. This can sometimes make it impossible to continue using that particular tool on that lock.

However, this is more common with softer brass locks like the Brinks than with steel ones.

The Three Types of Tension Wrenches

So we now have a solid understanding of the pros and cons of the tension wrench, but what about their characteristics?

Why are there several different types of tension wrenches and what is the difference between their slight variations?

Before we tackle the nitty-gritty details, let’s start by breaking the tension wrench up into three different types:

  1. The Straight Wrench
  2. The Twisty Wrench
  3. The Double-Ended Wrench
Note: There are other styles of tension wrench beyond these three, however, they're not as common and it's likely you will never use them. So to keep it simple we'll stick to these three types of tension wrenches!

1. The Straight Tension Wrench

First up is the straight tension wrench! This little guy is nothing more than a flat piece of steel with a 90-degree bend applied to a single end.

The Straight Tension Wrench

Now to fully understand the purpose and power of the straight wrench, it is absolutely critical that we understand three things:

Our turning tools provide us with more feedback – vibrations – than any other factor in lock picking.
We as pickers want to do everything in our power to use a turning tool that will provide us with the most feedback possible.
The turning tool that will provide us with the most feedback possible will be one that is the thickest and stiffest.

This third point is where the straight tension wrench shines brightest!

Because the straight wrench is a straight piece of metal it will not flex and will remain rigid while you apply torque to it, thus providing you with a maximum degree of feedback!

I understand that it can be kinda hard to put this into context without something to compare it to. So let's take a look at a tool that is the exact opposite of the straight tension wrench.

Something that is thin, floppy, and springy – the twisty wrench!

2. The Twisty Wrench

You may recognize these tensioning tools that have a 90-degree twist down the shaft. They are very popular and common in many lock picking sets.

The Twisty Tension Wrench

While these twisted wrenches have their benefits — which we'll touch on in a moment –, they are absolutely the worst wrench you could use to develop your skills. The reason being is that the twist acts as a spring and dampens the vibrations moving through the wrench.

To better illustrate this, think of the springs and shocks used in the suspension system of a car. If you were to hit a pothole, the springs will absorb and dampen the vibrations you feel as a driver. However, if you were to take out the springs and drive over that same pothole… well, let’s just say you as a driver would know you hit it.

Remember that when it comes to picking, feedback is everything. We want to feel every pothole, speed bump, and potential crack in the road as we metaphorically drive our lock picks up and down the pins of a lock.

So if the straight (non-twisty) tension wrench provides us with better feedback, why then would we ever use a twisty wrench?

Well, it can provide us with a pretty cool advantage that I like to call variable tension.

Because these wrenches have the ability to flex, the amount of tension being applied to the core can be controlled by us — the picker — AND, in some small degree, by the lock.

Depending on how we affect the lock with our pick, variable tension allows the core of the plug to more easily fight back – or what we call counter-rotate – and balance the forces on the lock. This is can be extremely helpful in situations like raking where the ability for the pins to slightly control the tension is way more important than feeling feedback.

Another slight benefit is that the twisty wrench can be more comfortable to use because your finger is resting on the flat side of the wrench rather than the edge.

3. The Double-Ended Wrench

Last up is the double-ended tension wrench.

This little guy is really nothing more than two straight tension wrenches packed up into one tool.

The Double-Ended Tension Wrench

Naturally, this 2-in-1 tool can give us the advantage of carrying fewer tension wrenches and can really cut down on the bulk of our everyday carry lock pick sets.

However, this benefit typically comes with a catch.

Because they are made out of a single piece of metal, both sides are typically the same thickness and width – making them identical in size. As you can see in the image above, the only difference between each side is usually the length.

So really the only question that remains is, "why is there a short end and a long end?"

Let's explore that next!

Longer vs. Shorter Tension Wrenches

If you pick up any set of tension wrenches, you'll likely notice that the tip that goes into the keyway will come in a variety of different lengths.

There is no better contrast to this variety than with the double-ended tension wrench as seen above.

So what is the purpose of longer and shorter wrenches and when should we utilize each?

Shorter Tension Wrenches

When using a tension wrench, you want to take up as little room in the keyway as possible. This also includes how far into the keyway your tension wrench reaches.

In most locks, you don't want your tension wrench to reach more than halfway into the keyway.

This is because the rearmost pins in the lock require the most leverage to lift.

The Tension Wrench - Leverage Behind Wrench

If you take up too much room in the rear of the keyway with the tension wrench, you may not have the leverage you need to fully lift and set a pin.

This is the sole purpose of shorter tension wrenches. To give you just enough metal to tension the lock, but little enough to still be able to maneuver your pick in the rear of the lock!

Longer Tension Wrenches

Master Lock 911 - Recessed KeywaySo if we ideally want to take up as little room in the keyway as possible, why would we ever need a longer tension wrench?

The reality is, there are quite a few locks that have some very strange features, including recessed keyways or something extruding from the face of the lock that would block our tension wrench.

In a nutshell, some locks need a tension wrench with a longer reach to appropriately and successfully tension them.

The Master Lock 911 is a great example of a lock that has both a recessed keyway and obstacles that extrude from the face of the lock.

While not radical, some shorter tension wrenches may not have the reach.

A good rule of thumb:

  • Short Wrenches: The keyway and lock features are flush with the face of the lock.
  • Long Wrenches:  Recessed keyways or any obstructing features extruding from the face of the lock.

That will about do it for length. Now let's tackle our final two characteristics – thickness and width!

Wrench Thickness & Width

Every lock is different in a variety of ways – including its keyway.

Some locks have small keyways and some have big. Some locks are tight with tons of warding, while others are wide and open.

The point is, there are a TON of keyways with different shapes and sizes. As a result, we need different sized tension wrenches.

When it comes to the size of the tension wrench that you use, it truly is a Goldilocks type of story.

If you use a wrench that is too small, you risk wedging it in the bottom of the keyway and binding the core.

If you use a wrench that is too big you may not have any room left to use your pick.

However, if you use one that is just right, it will tension the lock without binding the core AND you’ll have room to insert and maneuver your pick!

We’re not going to touch on how to select a specific size for a particular keyway in this article. We’ll cover that in another one soon, however, to polish this guide off let's quickly cover the typical measurements of most retail wrenches.

Most tension wrenches fall between .020" and .030" thick.

Additionally, there are typically three widths of wrench:

  • Thin: 0.1“ or 1.5mm
  • Medium: 0.11“ or 2.75mm
  • Thick: 0.13“ or 3.5mm

This being stated, there are many other widths available, but in general, most manufacturers offer some variation of a thin, medium, and thick wrench.

To Conclude

Like most things in life, the tension wrench truly is more than meets the eye! It is a simple tool with a complex nature that will never lose its utility – regardless of your skill.

The next time you pick up your tension wrench, take into account these qualities and try to merge them into your picking. By simply understanding and taking advantage of these characteristics you can truly use the tension wrench to its full potential.

And if you are just getting started with lock picking, remember that you ideally want a tension wrench that will provide you with the most feedback possible – such as the straight wrench. However, don’t let that stop you from playing around with other variations of the tool!

I hope this long-winded guide put a little more perspective behind the tension wrench and hopefully answered every question you may have had.

If you have any questions or comments about this guide or other topics, be sure to drop that in the comments below or throw me an email here. I always love to hear from you guys!

Happy Picking!

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