How To Make a Spy Gadget

by | Spy Gear

Last Updated on March 10, 2021

There’s certainly no shortage of spy gadgets you can buy today. Some are more expensive, some are cheaper, but most of them do their job. The thing is, many of us don’t really want to buy things outright, but would rather go DIY. In this scenario, knowing how to make spy gadget can be an interesting skill.

Now, to be honest, being able to make complex spy gadgets that require a lot of electronics isn’t something many of us could do. However, there are some simpler gadgets that you can do pretty easily. Therefore, below we’ll talk about a couple of them, and we’ll show you how to make them.

Well if making your own isn’t an option, check our best spy camera and start spying this instance.

A Keyhole Peeker

This is the simplest one of them all, and is something just about anyone could do. All you’ll need is a clear marble, thick black paper, scissors and tape, and you will be able to look through a keyhole and see the entire room on the other hand. Note that the marble should be small, so it fits through a keyhole.

All you’ll need to do is set the marble’s center on the paper’s edge. You should wrap the paper around the marble, in a tube shape, but have half of the marble sticking out. Sticking it is also an option, but basically you want a cylinder with a marble on one end, and half of that marble sticking out.

When you’ve found the keyhole, you should push the end with the marble inside the keyhole. Look through it, from the other side, and you should be able to see an upside down version of the entire room. Pretty cool, right?

Invisible Messages

Every good spy will need a way to write a message that nobody except the intended recipient will be able to see, right? Well, this is certainly a possibility, and it’s a lot easier than you think. All you’ll need is some lemon juice, which acts as the invisible ink.

Make sure you have some of it in a container. Whether you buy it or make it yourself, it doesn’t make much of a difference. Once you have it, you should grab a paintbrush, or a cotton swab, and write your message on a piece of paper. When the juice dries, nobody will be able to read the message because it’s going to disappear. However, if you were to warm up the piece of paper, with a radiator or an iron, the ink will turn brown.

One thing to note here is that you might be tempted to heat the paper with a candle or a lighter. This isn’t really a good idea, because this way you can easily set the paper on fire, and destroy your message. Exercise caution here, and you’ll get your invisible messages.

This is arguably one of the coolest things you can make, and the one that most resembles something spies used to use in the past. In terms of materials, you’ll want a pen or pencil, thick paper, a paper fastener, scissors and a ruler. This isn’t a lot, and the technical knowledge required is also not that big.

First things first, grab that piece of paper and draw two circles. One of them should be a few centimetres smaller than the other one in terms of diameter. Once you’ve done this, you should cut those two circles out. Poke a small hole through each circle’s middle point, and use the paper fastener through that hole in order to join them.

Then, grab your ruler, and divide the circles in 32 segments each, like 32 pizza slices. The easiest way to do this is to divide it in half first, then continue doing this, splitting each segment in two. At this point, you’ll have two circles, each of which has 32 pieces.

Write the alphabet, one letter per segment, on each circle. You’ll have a few segments leftover, so you can add a few symbols there if you want to. And that’s about it. Now you have every letter in the alphabet replaced with another letter, and you can write coded messages that can only be decoded using that same cipher wheel. (1)

A Book Compartment

If you’re looking for a small place where you’ll be able to hide a few things, a book could be a great option. Before we get into this, note that you’ll basically destroy a book that’s thick enough to fit all the things you need, so make sure you’ve got one you’re willing to spare. If you still want to continue, it’s time to grab the tools you’ll need. Take a pencil, a hardcover book that’s thick enough, a ruler, and a box cutter.

Open the book a few pages in. Some would suggest that you keep around an 1/8th intact, on each side. Grab the pencil and ruler, and draw the opening you’ll be cutting. Don’t make it too close to the edges, because you can easily mess things up like that.

Start cutting, and make sure to take things slow. A good suggestion is to use adhesive that will keep the pages together, because that minimizes the chances of you cutting through the entire page and destroying the entire book for nothing. Once you’re done with this, you can store anything important that you’d like to hide inside the book. Just be careful when opening it!

Wrapping Things Up

Contrary to popular belief, spy gadgets aren’t limited to high-tech items that do things like recording voice and video. There are a lot simpler items that were (and sometimes still are) used all around the world, and above you’ve got a few of them that you can actually do by yourself. They’re pretty simple, require minimal know-how, and you’ll get a surprisingly useful spy gadget that could come in handy.

If you have the camera already, here are some great spy camera ideas you can check. But make sure you don’t violate laws by using these, and it would be better if often you educate and ask yourself with spy camera ethics, is it ethical to use one? I hope this learning guide helps! Til’ next time! 


(1) – Alberti Cipher Wheel –

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About Gadgets Spy

Hi, I’m Michael, a security and surveillance expert. I co-founded and write for GadetsSpy and help teach people about new tech and Gadgets.