When checking into a hotel, most of us glance around for cleanliness, inspect the bathroom, or make sure the lights work — but there’s one spot travelers often miss: under the bed. It might seem insignificant, but that hidden space can reveal a lot about both safety and hygiene. Esther, a Dutch flight attendant for KLM, recently shared a clever trick she uses every time she checks into a hotel — and it only requires a water bottle.

Before unpacking, she simply tosses a water bottle under the bed and watches how it moves. If it rolls straight out the other side, the space is clear. But if it stops suddenly or doesn’t emerge, it could mean there’s something underneath — maybe luggage, trash, or in extremely rare situations, someone hiding. It’s a quick way to ensure nothing unexpected is lurking where you can’t see.

If the bottle doesn’t roll through, Esther advises not to bend down and check yourself. Kneeling to look puts you in a vulnerable position. Instead, keep your distance, step out, and alert hotel staff or security to inspect the area with you. This small precaution gives you time, awareness, and safety — especially useful for solo travelers or those arriving late at night.

Beyond security, this trick also doubles as a cleanliness check. Under beds are often skipped during quick cleanings, collecting dust or pests. If the bottle picks up dirt or doesn’t move freely, it might be worth requesting a new room or a deeper cleaning. It’s a simple, practical habit that offers both peace of mind and a safer, cleaner stay — proof that sometimes the smallest actions make the biggest difference when traveling.