Untangling the Christmas tree lights after a year being tucked away in the loft is a dreaded but necessary task households face each December.
And to make matters worse the lights often don’t work when you plug them back in, forcing you to hunt for a spare fuse bulb to get them going.
But it’s not just the fuse bulb on your lights that has a special purpose, as the red tipped light bulb also serves an important function.
If you’re wondering what the small red bulb is for, you’d be wrong to assume that it’s a spare to replace a bulb that’s gone out.
You might be surprised to learn that the bulb actually has a greater purpose and is used to make the lights on your tree blink and twinkle.
The extra light also changes the whole look of all the other lights and when inserted into a regular set of lights produces a flickering effect, which is handy for sets that don’t have a modern remote to change modes.
Explaining its surprising use on TikTok, user Kendra Hagerman said: “Have you ever wondered what this little red bulb that comes with your Christmas lights is for?
“It is not an extra – I always thought it was until I recently found out that it actually has a really cool feature.
“It makes your lights flash! No timers, no extra gadgets, this is the old fashioned way. Did you know about this?”
Equally stunned viewers shared their surprise in the comments, with many admitting they thought the bulb was a spare and had always thrown it away.
One person wrote: “What?! After all these years of putting it in the garbage.”
Another said: “I thought they were extra if one goes out therefore I always throw them in the garbage.”
A third added: “Whaaat daammn I was today years old.”
However, some viewers admitted that they had been aware of the red light’s little-known use for years and were surprised people didn’t realise what it was for.
One person said: “Are you KIDDING? This is common knowledge and has been this way for decades. The red bulb makes the lights blink. Come ON. Read the box.”
Another added: “Knew this like 40 years ago.”
A third wrote: “Yep my grandma taught me many many years ago.”
