In our apartment in China 🇨🇳, my slippers are allowed to travel almost anywhere. Except outside the front door. And if they do venture into the corridor, they must be cleaned before being permitted back inside. My Chinese wife takes border security very seriously. Let me explain. Like many Chinese households, ours has a strict division between outdoor shoes and indoor slippers. Fair enough. Nobody wants to bring the dirt from the streets into their home. But our apartment is on the eighteenth floor, and there's a communal corridor leading to the lifts. Surely, you might think, stepping into that corridor in your slippers wouldn't cause much trouble? You would be wrong. According to my wife, the moment those slippers cross the threshold, their soles become contaminated. Before they can return to normal domestic duties, they must be wiped clean. I've occasionally wondered whether the slippers themselves appreciate the distinction. After all, they've travelled only a few metres across a tiled floor. But today I received a rather illuminating lesson in why my wife takes these matters so seriously. When I returned from work, she was complaining about the community ayi, the cleaner responsible for mopping the communal area by the lifts. Apparently, the ayi wasn't cleaning the floor at all. She was simply swishing an already dirty mop around, redistributing the dirt rather than removing it. My wife was not impressed. In fact, she'd become so annoyed that she went and cleaned the area herself. And then complained to the management company about the standard of cleaning. I began to understand why my slippers were regarded with such suspicion. That innocent-looking tiled corridor was apparently a hazardous border crossing. And the official responsible for keeping it clean had failed her inspection. Now, I have no particular objection to keeping our apartment clean. Quite the opposite. But I do find the whole business of slipper border controls rather amusing. In Britain, I don't remember worrying about whether my slippers had crossed an invisible line between domestic cleanliness and communal contamination. Here, the distinction is apparently very important. And I've learned that arguing about the cleanliness of slipper soles with my wife is rather like arguing with airport security. You may believe you're making a perfectly reasonable point, but you're not getting through until you've complied. So I remove my outdoor shoes, wear my indoor slippers, and wipe their soles whenever they've been on an unauthorised excursion. Domestic peace is a wonderful thing. Although I suspect the slippers are beginning to feel rather oppressed. So, readers, does your household have similar rules about indoor slippers? And would you trust a communal floor that had just been cleaned with an already dirty mop?