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How It Works: Intruder Lock Function on Grade 1 & Grade 2 Commercial Locks


Learn how Intruder Locks (Grade 1 & Grade 2) function by viewing the video above or reading below.

Unfortunately, these days schools and businesses are looking for innovative security devices that will protect their staff and students in the case of an intruder or unauthorized person gaining access to the building. The Intruder Lock Function allows a door to be locked and unlocked from the inside of the room as well as from the outside, thus providing an extra layer of protection during a security alert or school lock down situation.


To begin, let’s review the difference between the different grades of intruder commercial locks that are available. Each grade of lock specifies a certain load per inch. Grade 1 locks are made to withhold the most weight, followed by Grade 2 and Grade 3 at the lowest weight threshold.

Below are the specifics of each commercial lock grade. At CLK Supplies, we sell both Grade 1 and Grade 2 commercial intruder locks. Clicking the links below will take you to the full list of specifications and product page for each type:



In highly stressful situations such an office or classroom lockdown, teachers and staff need to be able to quickly add an additional level of security. Commercial intruder locks function in a way that allows the door to be secured from the inside of the room.

Unlike a standard door lock mechanism that will not move when the door is locked, the lever handle of a commercial intruder lock will still move up and down even when the lock engaged. To unlock and lock a commercial intruder lock in a non-threatening situation, the key must be placed in the keyhole on the exterior side of the door and rotated 360 degrees to the right to lock and to the left to unlock. Locking a door from the outside is the function of any usual door lock.

Intruder Lock Functions

The added benefit of an intruder lock is that no matter what the exterior door lock is set to (locked or unlocked), an individual inside the room can use a key to lock and unlock the exterior door lock from the inside. By locking inserting the key and rotating it 360 degrees to the left, a teacher or staff member can set the door to remain locked outside while leaving it unlocked on the inside. This prevents any entry into the room from the outside while keeping it unlocked to those leaving the room. Used on a regular basis, commercial intruder locks add an extra level of security that keeps danger locked outside while providing a way for escape that doesn’t require too much thinking. The door is locked from the outside by default, can be propped open during usual hours but very easily closed with automatic locking for security.

Intruder Locks from the Inside

These days we can’t be too careful about adding every security measure possible to keep our staff and the students in our schools, safe from harm. Commercial intruder locks function in a way that adds an almost automatic additional level of safety.

If you found this post and video interesting stay tuned for more on key products for the security and locksmith industries. At CLK Supplies, our goal is to provide key people with the highest quality product available at the right price, and with our 'hands on, get it done' approach. Our first class "gold" service is important to us, knowing our customers are working long hard hours making sure their customers feel safe.

You can view the full video for this post on YouTube here: Don’t forget to like and subscribe to our channel where we upload new tutorials on locksmithing every month.

Video Transcript:

Hey, this is PJ with CLK Supplies, and this is the Intruder Lock function. Now this lock function is found on grade one and grade two commercial locks. Now just like its name, the intruder lock function is designed to be put on situations where a lockdown or a safety situation comes up and you need to build a lock the outside of the door from the inside of the door. Let me show you how it works. Now this is the outside or the exterior side of the lock, and as you can see right now it is locked. This is a clutch function lever. I'll put a link in the notes below, but when you pull the handle down, it's not moving the latch here. So just like a classroom lock, when you turn the key 360 degrees, it's going to unlock it. Now it's going to stay unlocked until you put the key in, turn it 360 degrees and now it's going to stay locked.

Now on the inside of the door, as you can see here, this particular lock has a laser engraved lock with the arrow that's pointing counterclockwise. So that's really there to help in the event of an emergency situation. You don't have to think about which way to turn the key to lock the door from the outside. Now some locks don't have this on here and I've seen... Sometimes I'll just take a Sharpie and write it on there, but it's really nice on this particular one that has it engraved on here. So what you're going to do, so on the outside of the door here, as you can see, it's locked. I'm moving it down and the latch isn't moving.



Engraved lock/unlock for Intruder Lock

Now let me unlock this here real quick. It's like that. All right, so now it's unlocked. Now from the inside of the door, let's say you have a lockdown situation, all you have to do is put the key in just like that, turn it 360 degrees in the direction of the arrow, which is counter-clockwise, and you're going to see from the outside of the door, it is now locked. And that's really what this function is all about, is being able to turn the key on the inside to unlock or I should say lock the door from the outside. Now, in the meantime, on the inside of this store, on the inside of this lock, it's always going to be unlocked. So you're never going to be locked out in this situation.

This key here is really only to allow you to lock the outside or the exterior of the door when needed. So that's the intruder function. Thanks for watching, I'll see you next time.

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