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  1. Padlocks
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Master Lock Stainless Steel Padlock with Shielded Shackle - 3/8" Diameter Shackle

Master Lock Stainless Steel Padlock with Shielded Shackle - 3/8" Diameter Shackle

Item # ML40D
Our Price: $27.68
Orders above $99 qualify for Free Shipping
Shipping Weight: 0.63 lbs
In Stock
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Great Prices for the best padlocks from Master Lock. Master Lock Stainless Steel Padlock with Shielded Shackle - 3/8" Diameter Shackle part number ML40D can be ordered online at or call 1-800-940-8924 for expert service.
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Master Lock Padlocks - ML40D

  • 3/8 Inch Diameter
  • Universal Application Padlock
  • Keyed Unique
  • Master Lock
  • Stainless Steel


  • Shielded padlock protects shackle and your gear
  • Hardened steel shackle for extra protection
  • 4-Pin lock cylinder is pick resistant
  • Key can not be removed unless the padlock is locked
  • Stainless steel body resists corrosion


  • Overall width: 2-3/4"
  • Shackle diameter: 3/8"
  • Shackle length: 3/4"
  • Opening with shackle closed: 5/8" tall x 3/4" wide

40D - Kit Master Lock Stainless Steel Padlock with Shielded Shackle - 3/8" Diameter Shackle

Video of Master Lock Stainless Steel Padlock with Shielded Shackle - 3/8" Diameter Shackle

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Master Lock Stainless Steel Shielded Shackle Padlock Review

Everybody, welcome to I'm Bobby, and today we're taking a look at the Master Lock stainless steel padlock with shielded shackle. Now this is gonna be an excellent way, guys, of going ahead, securing maybe a latch on this kind of trailer, as you guys can see. Now one thing that's great about it, it does have this shielded shackle. And now that may make it a little harder to get on some accessories, but as you guys can see, it's really easy just to go ahead, turn that key, and there we are, nice and locked in. One thing that is a little unique about it, you actually can't remove the key unless it's locked.

So you are gonna know that it's nice and secure when you remove that key. Now, the shielded shackle here is gonna give you a little bit more protection, as you can't actually find a place to actually get any cutters to start messing with our shackle. Now, the stainless steel construction on this is gonna be excellent to go ahead and make sure we can leave it out here in the weather with no troubles, which is excellent. As, of course, is too with the tumbler being nice and recessed in there. I don't think we're gonna have any issues with anything kind of debris building up on there, which is excellent.

Now the one thing I will say, though, because we have that shielded shackle, we are gonna be a little limited on our spacing. We only have about three quarters of an inch spacing here between us to actually get this on any of our latches. Well, you can kind of compare that to some other padlocks out there, which are more closer to an inch. So speaking of that small diameter we we're talking about, you guys can see we have just a little cable out here that has two hoops and need to be connected by a padlock. Gonna be a little harder for me to actually get this to work here, so I'm gonna have to try to hold it and then flip it.

Now it is working, right, and you can see that was a little bit more difficult. Now compared to similar more traditional padlocks, those guys just have an easier time 'cause they are a little bit lighter. Now the one thing I think this one will really struggle with too, is if you have a lot of points of entry, like this trailer. So, gonna be hard to get all of these keyed alike, and at that point, you're messing with three new keys on your key chain. I might suggest taking a look at some other padlocks here with some key alike options.

One that comes to mind is the Bauer Products padlock. That's gonna give you a lot of great key alike options. But, if you do have only single-access stores, this is still gonna be great. Overall, guys, I think this is gonna be excellent for a lot of your flip down latches or a toolbox, something that only has one entry point, or if you have a single access point on your trailer that can be great. But overall I still think it's gonna do a great job. I really like how hefty the stainless steel is on here. I know it's gonna be lasting me for the years to come, which is great, and honestly I don't think anybody's gonna mess with this. I'd take one look and I'd go, "No thank you." So I think that about does it for our look here at the Master Lock stainless steel padlock with shielded shackle, here at your I'm Bobby. Thank you for watching..

Customer Satisfaction Score:

Customer Reviews

Master Lock Stainless Steel Padlock with Shielded Shackle - 3/8" Diameter Shackle - ML40D

Average Customer Rating:  4.6 out of 5 stars   (77 Customer Reviews)


As per selection offered by of three discus Master padlocks with 3/8" shanks keyed alike, we are very pleased with the quality of the product received, as well as the fact that no hardware stores in the Reno/Sparks NV area carried a three pack of these types of locks keyed alike. This makes for very simple ease of use in our situation as well as having the security of discus locks in our application.

Also, no hassles or issues in ordering these locks on line. Delivery info on web site was straight forward, accurate and timely. Will considering using again in the future.

Fine. Thanks for your concern! Good product!
Sue - 02/20/2019


This lock worked great to secure my trailer hitch anti-theft device. I would definitely recommend it.


Secures the coupler locks and the spare tires on all of our trailers...make sure to remember to check the keyed the same no matter what truck or tractor key ring you happen to have on you, you'll have that same trailer lock key...:)


Clumsy and sticky to lock and unlock. I ended up putting a dry lubricant in the lock to get it to function smoothly. I am conerned that under adverse weather conditions the lock may not work smoothly. etrailer was terrific, arrived quickly, no issues, all locks properly keyed. I still use etrailer and it has been an excellent resource for trailer issues.


I recently purchased this lock for my etrailer trailer hitch lock and they both are so very easy to secure and it gives me peace of mind knowing that these items are very safe and VERY easy to use!!

I would strongly recommend these items for anyone who wants to know that his/her horse trailer is not going to be stolen!

Thanks etrailer,

Kathleen D.


This trailer tongue lock is easy to use and it is just grand that the same key works on the tongue lock and ball latch!!

I have been buying all of my trailering accessories from these folks for years and I will continue to do so since they have a great products, are knowledgeable, and provide great customer service!

D. Link


tire and lock was what I needed to finish up my paint trailer to put it in service. E-Trailer is a outstanding company to deal with price was great and customer service was outstanding A+++++ on getting shipping problem handled. Thanks again E-Trailer for a great product will use you again for sure


Got exactly what I paid for. Nice masterlock disk locks all keyed alike. Thanks a bunch!

Great. I purchased 13 of these using in a laundromat and havent had issues with any of them. Still very happy with the purchase.
JustinV - 12/14/2017


This is a great design - very difficult to attack w/bolt cutters - and was able to ship me 5 of them keyed alike to cover my entire trailer.

One thing I would like to see - a simple sleeve, made of the soft silicone such as cell phone skins, in the shape of this lock. That would help keep the elements out and prevent metal-to-metal contact against the trailer.


The Locks worked very well on the doors but are to large for the tongue.I wish they nade one to fit it.


We travel to several states for horse shows. We purchased this padlock to use with our E Z 5th Wheel Lock. These items sure provide an added sense of security.


etrailer was able to help me buy 5 keyed alike locks. My experience is that etrailer's customer service is great and they're competitively priced across their entire product offering!


Fits very well, and makes me feel much better about leaving my trailer parked. We have had many trailers stolen from farms in this area, so it was imperative to get a sturdy locking system.

Thanks for your product and fast service.


What a great combination!
The Baylock
EZ lock is much better than what was available at local shops.
With the Masterlock, which fits perfectly, I feel that my trailer is as secure as can be; thieves are inventive!
Would highly recommend this setup.


Excellent trailer coupler lock!
design makes attachment quick, easy and tamper resistant.


I will be towing an enclosed trailer loaded with some rather valuable items on board. These locks fit the trailer hasp's perfectly I am totally confident in their ability to keep my goods on board and safe!
Thank You etrailer again!


REally like these locks which I have now used for a year. I cannot see how anyone ( normal demented crook) could break this lock. My trailer is super safe with this lock securing the coupler. Highly recommend.


Ordered 3 locks keyed alike. Very prompt shipping and the price was right. Smooth working mechanism and fit the trailer perfect. Kind of disappointed that they were made in china, but what isn't these days. Very satisfied with product and


Arrived on time. Coupler lock made well and lock is good also. A friendn of mine has a trailer coupler lock, easy to use and locks the trailer up good.


Great lock for my gooseneck. Quick and easy to order!


Fit my enclosed car trailer rear door perfect and matching keys a plus for sure :)


We ordered 2 of these locks to replace locks already used in our fleet. Specificially we needed them keyed to match our other locks as identical keys are already used by over 50 people within our company. The customer service team was great, assuring they would cross check their inventory for locks coded to the right key or specifically order them in for us. They had them in stock and sent them to us right away, and everyone's pre-existing keys work in them perfectly. THANKS FOR YOUR HELP!


Products as described. Ordered on Monday and they arrived on Wednesday! Ordered two sets of wheel locks and they were "keyed" the same without even having to ask! Excellent responsiveness and follow-up.


I bought this as part of a complete tow package that I needed to install. Not only did I get everything I needed and verified by customer service, but they also made sure it was rush shipped to me during Christmas weekend. Awesome products and service!


Heavy Duty lock, works well with EZ Lock Trailer Coupler.

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