A thread you can barely see on your front door — police warn it could be a burglar’s trick

At first glance, it can look like a strand of cobweb caught between the front door and its frame. Police are now asking residents to take a closer look.

The method has been documented by several police departments as well. You don't have to panic, of course, but with darker evenings returning, it is one small detail that may make the difference between keeping your home secure and leaving it vulnerable to intruders.

How the thread trick works

Police in Hamburg have issued warnings about so-called “absence checks”: burglars placing barely noticeable adhesive threads or small pieces of plastic between a door and its frame. If the marker is in place for longer stretches of time, it suggests the door hasn’t been opened, and the residents may be away.

The idea is surprisingly simple. A very thin adhesive thread is stretched between the door and frame. In some cases, small pieces of plastic are used instead.

When somebody opens the door, the thread breaks or the plastic falls away. If everything remains untouched for hours or days, burglars may take that as a sign that nobody is regularly entering the home.

Berlin police have previously described the threads as spiderweb-like and difficult to see with the naked eye. A flashlight can make them easier to spot, while the glue itself may appear as a small round dot on the door or frame. Police there have linked the method to burglars scouting apartments before attempting a break-in.

This isn’t an entirely new idea. Burglars have previously used paper, tape and other small markers to check whether a door has been disturbed.

What should you do if you find one?

Don’t assume a random cobweb means burglars have targeted your home. But if you notice an unusual thread deliberately fixed between the door and frame, particularly alongside small glue marks, it is sensible to document it before disturbing it.

Take a photograph, check nearby doors if you live in an apartment building, and let your neighbors know. Police advise reporting suspicious markers rather than simply brushing them away, because they may be useful during an investigation.

If somebody suspicious is outside your home or you believe a burglary may be in progress, contact emergency services immediately. In the US, non-emergency numbers vary by local police department; call 911 when there is an immediate threat or a crime is in progress. UK readers can use 101 for a non-emergency police report. In the Netherlands, use 112 for emergencies and report non-emergencies on 0900-8844. In Belgium, the police emergency number is 101.

Dark evenings make ordinary precautions more important

Police recommend locking windows and doors even when you leave briefly, actually turning the key rather than merely pulling the door shut, and leaving a light on when you are out after dark. A timer can make that easier. Valuables should stay out of sight, while shrubs around the home are best kept low enough for neighbors to see the property.

Those precautions still matter despite a long-term fall in burglary. CBS figures show that Dutch police recorded about 21,600 residential burglaries in 2025, down from almost 88,000 in 2013.

Belgian and US police give similar advice, including using timers to switch lights on in different rooms and making a home look occupied while you are away. Many police zones also provide holiday or absence checks, although arrangements vary locally.

So there is no reason to inspect every cobweb with suspicion. But if you spot a strange, tightly stretched thread exactly where the door meets the frame, taking a photo and reporting something genuinely unusual is a sensible precaution.