Borromean zip ties

Time to connect with a maths activity! Get hands-on to learn more about chains and ancient links.

You will need

3 zip ties
A good pair of scissors
An example of chain – such as a dog leash or a chain fence

What to do

Take a zip tie and feed the skinny end through the slit at the other end. When a few centimetres are pushed through, it should catch so it can’t be pulled apart again.
Feed the third tie over the top loop and under the bottom one.

Take a second zip tie, and make it into a loop like the first.

Put the two loops on top of each other, with the top one to the left and the bottom one to the right.

Take the third zip tie and weave it between the two rings. Working left to right, the third zip tie will go over, under, over, under.

Join the third zip tie up into a loop. The three zip ties should now be all stuck together!

Move the rings around, and look at how they are linked. Compare it to an example of chain. How are they similar or different?
Going left to right, the third tie goes over, under, over, under.

To destroy the rings, choose any one of the zip ties and cut it open. Do the other two stay linked?

What’s happening?

In a chain, two adjacent links go straight through each other. In this activity, none of the zip tie loops go through each other, but somehow they stay stuck together.

This set of three connected rings is called Borromean rings, and there are illustrations of it over 1000 years old. You can’t take three existing rings and weave them into this arrangement – you need to break at least one ring to link them in this way.