Unfortunately, the change of season has brought an unwelcome new feature to my home: mice. Not quite as stylish as burnt-orange curtains, these new autumn accessories are very much not welcome. A few weeks ago, my roommates and I started spotting the telltale signs that we might have a mouse problem.
There were scratching noises at night, gnaw marks on the skirting boards, and, most upsetting of all, small, dark, pellet-shaped droppings in our kitchen cabinets. The memory of finding them still makes my stomach churn. Naturally, as a household advice writer, my roommates turned to me for help—so I showed them the pencil trick.
If you suspect you might have some unwanted houseguests of your own this fall, the pencil trick can help you spot potential entry points before mice get properly settled in. We combined it with a couple of other reliable measures, and we haven’t seen a mouse since. Here's how it works.
What is the pencil trick?
Mice are surprisingly good at squeezing through tiny gaps—and that’s quite the understatement. Mice can easily fit through an opening as small as 5 millimeters. That’s roughly the width of a pencil’s eraser. Mice have soft, pliable bodies and don't have rigid, locking collarbones. Their sloping, flexible skeletal structure lets them compress their bodies to flatten out and slip through tight gaps. Truly the stuff of nightmares.
But this pencil reference is a key fact to remember. It gives you a handy way to judge whether a gap might be worth investigating. It won’t tell you for certain that a mouse has used that route, but it can help you spot places where one could be getting in, and therefore where to focus your attention.
How to do it
Take a slow look around the edges of the room, especially where pipes or cables enter the wall, under doors and behind appliances or cupboards—pencil in hand for referencing. If you find a gap around the width of a pencil’s eraser, mark it so you can come back to it. I found it helpful to check the spots we’d usually overlook, rather than just staring at the middle of the kitchen and hoping to catch our tiny, whiskered culprit in the act.
Once you’ve identified a likely opening, seal it with a mouse-resistant material. BPCA recommends packing small gaps with wire wool and securing it with quick-setting cement—which is exactly what I did in my own home using the below materials. For a larger or awkward hole, it’s sensible to ask a pest controller or tradesperson what’s suitable. Don’t block air vents or air bricks, as these still need to ventilate, and you’ll want to make sure whatever material you plug the holes with isn’t edible to mice. They will chew through a surprising amount of things, such as plastic filler, silicone or other soft sealant, plastic mesh, wood, and rubber, which is why you'll need a combination of expanding foam and steel wool to really stop them in their tracks.
Other measures to take if you suspect mice
The pencil trick helps you look for a way in, but if you’re already seeing droppings or hearing activity, take a few other steps, too:
- Put food away. Move open packets of cereal, pasta, rice, and snacks into sturdy, sealed containers, and wipe up crumbs as soon as you spot them. Check behind the toaster and under cupboards, too—it’s easy for little bits to collect in places you don’t normally look. Don’t leave pet food or food waste out overnight, and make sure your bin lid closes properly. Mice are persistent little scavengers, so even a small, reliable food supply can encourage them to stick around.
- Check likely hiding spots. Look under the sink, behind the fridge and cooker, and around the back of cupboards for droppings, gnaw marks, or shredded paper and fabric that could be nesting material. These tucked-away spots can offer warmth, shelter, and easy access to food. If you find fresh signs in one area, make a note of where they are; it may help you work out where to focus your next steps.
- Get help if the signs continue. One mouse can quickly become a bigger problem, so don’t ignore fresh droppings, new gnaw marks, or continued scratching noises. If you’ve taken steps to remove food sources and address likely entry points but the signs persist, contact a pest control expert. If you live in a flat, let your landlord or building manager know, too, as mice may be getting in through a shared wall or another part of the building.
As the Household Advice Writer, Ella covers all things home – from clever cleaning tips to the organisation tricks that really do make life easier. Before joining Good Housekeeping, she was a full-time freelance writer and production journalist at The Independent’s IndyBest reviews section, where she covered reviews, roundups, and product-related news articles, focusing on areas such as homeware and lifestyle products. With a keen eye for what actually works, she’s passionate about sharing practical, well-tested advice you can rely on. You can reach her at her email address: [email protected]
