Picture of Twin Lock Box
“Twin Lock Box” is a wooden combination lock puzzle box that I designed. I applied the mechanic of my “Tricky opening bottle” to this box.

This puzzle box has five keys on both side. You must push all wooden keys to correct position for opening the box. After opening the box you can change order of keys and you can make your own box configuration.

I designed an other variant of this box with hidden keys. This variation has a fixed key configuration. You can see my other puzzle box and puzzle designs from my blog “Diypuzzles” and you can find a lot of free plans.
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Step 1: Box mechanism

Picture of Box mechanism
On both side of the box there are 5 wooden sliding key. Each key has two position and can move until the borders of the box. After opening the box you can remove all keys and you can make your own configuration by changing their order. If your friend have the same box, he can't open yours.

This puzzle box has three main section
1. Wooden keys
2. Box
3. Box cover

I started to make this puzzle by making wooden keys. After I made box and box cover.

The overall dimensions of this box is about 70x82x150 mm. But I advise understanding the design and making your box according to your materials an the dimensions. This is a simple design for converting dimensions.
nitrous3 years ago
Great project. Very clear instructions and very well documented.
What did you use for your graphics?
I used google sketchup
puzzlerhan (author)  nitrous3 years ago
Thanks, For 3D graphics, I made a model of the box in "Google sketch up" A free 3D design software and I take photos with a screen capture software "Screenshot captor". But mostly, first I design my puzzles in 2D with "Draftsight" a free "Autocad" alternative.

can you figure out the combination by pulling up on the lid and playing with the keys until the slip into place

Definitely not, if all but one key is "in place" , the box will feel the same as if it's fully locked, unless strong force is applied in which keys CAN break. But that's not solving it is it
puzzlerhan (author)  gumbo.gumbo.1046 months ago
By pulling up and playing with keys, you can try to guess correct position for each key. But until all keys comes to correct position , the box cover will not move. This method is a little locksmith work.
okay I made one and designed a solution so that method will not work
puzzlerhan (author)  sam.hendley.75 months ago

I made one from this box and a lot of people made this project and shared photos on the web. There isn't a design problem. If you give more information about your problem, may be I can help you.

Thank you this was a good project.
jordan.choy made it!5 months ago
I made this box as a Christmas gift for my girlfriend and it turned out amazing! See picture attached. I also added false walls on the inside to prevent items from blocking the lock mechanism, but be careful because there has to be plenty of room for the peg board to slide into place, even if they are slightly tilted inward. I used the tips of wooden golf tee's as the pegs, for a pointed peg. I also added a "code" on each key, so that she can figure it out if she forgets, but it's not SURE obvious to the random observer. I've tested it on friends too, they didn't notice the colour coding on each peg (red or black, depending on 'in' or 'out' position required. Thanks so much instructables ! If anyone has questions reply here and I'll try and check often enough

Built my grandpas casket the same way,,,,, unfortunately it was a closed casket as My uncle who helped me with the locking mechanism while in one of his lucid times had an Alzheimer's fade out at the time and forgot to tell the funeral home how to open it. And every time we asked he would mumble something about the Bataan death march, unripe bananas and Hitler starting the group, Rammstein


Great project!

If you want to make the tumblers reversible (so you can have any number of either position) you can instead cut a groove along the tumbler's center line. This may in fact be easier, since you can take the entire piece of stock and dado the grove down it, although you would have to attach end caps to the tumblers to prevent an attacker from being able to physically see the tumbler arrangement.

griffin292 years ago
Really love this and I enjoyed looking at your blog. Might need something easier to start with as my woodworking skills are a bit poor but might just go for it.
ok im building one of these this weekend.... wish me luck!
o22sanjo173 years ago
lil bit confusing,bt nyc one
bogrider9043 years ago
quite impresed
i am only a teenager but am quite interesting in engineering and wood work
i am always looking for other ways to store valuble stuff sequrely and this will go on my list to make
thanks alot
very nice! I will be building this at some point!