I get out of the taxi on a highway offramp. The driver, from Dongguan, doesn’t want to be on the surface streets of Shenzhen. After a week on the road I don’t mind, and I shoulder my backpack and duffle. I weave through stopped traffic to the curb, following it down to ground level. The border is less than a hundred meters away, a large building that houses Chinese customs connected to a walking bridge across the river to another building that houses Hong Kong customs and the Lok Ma Chau train station.

I’ve walked further to borders.

Carrying gear through traffic on the surface street I pause on the dotted yellow as cars start to move and pass on either side. It’s an action that would cause problems in San Francisco or New York but here, like so much of the world, is simply part of crossing the street. Three cars later there is a gap and I am on the far sidewalk. Five minutes later I’m in line for exit customs. Five minutes after that I look at the river that separates Shenzhen and Hong Kong. Like always it makes me realize how small the differences are between places and how much impact they have on our lives.

Borders are largely artificial. Yes, the river forms a nice demarcating line, like the Rio Grande between Texas and Mexico, but the differences in income, opportunity, language and safety are not caused by the river.

On the train into Hong Kong the air is already slightly better. Pollution does not respect borders, but the sources of it do. Hong Kong’s air has worsened over the last decade due to its proximity to Shenzhen, Dongguan, and the whole Guangzhou region, but it’s still better than those cities. So too is the food, Internet, and transit, not to mention salaries. The effects of man. Housing is more expensive though, so many Hong Kong residents have started living in Shenzhen, commuting across the border to take advantage of the artificial cost disparity.

Walking this border is new to me. I first crossed it on foot less than a year ago, though the lines and shops have grown familiar with frequent repetition. Without an electronic ID card I have to wait in line, unlike my commuter friends. It’s still an amazingly efficient border, on both sides. Hong Kong customs are rightfully considered a model, fast, well-organized, and simple to cross. Being a trading port and an international hub requires good customs, I think.

Less than one year. Surprising to me, as it feels like much longer. Fourteen times at least. First with others, colleagues and factory representatives. Then by myself, often met on one side or the other. And now, in a taxi I found, dropped on the off ramp from the highway.

The borders we cross say a lot about our lives. As a boy from upstate New York, the frequency with which I walk the Hong Kong Shenzhen border serves as a shorthand explanation of my job, checking factories and working on manufacturing problems. It also outlines another, more common border I frequent: that between San Francisco and Hong Kong, delineated by airports and the Pacific. This border, seemingly unremarkable, is of course the slowest to cross, and the most expensive. Impossible on foot, or as a daily commute.

Two years ago my border crossings were very different, the product of another job, another life.

In that life I stepped out of the minivan into the harsh light of a Juarez autumn. I carried less, just my backpack, and walked faster through traffic, uncertain of its comfort with mid-stream pedestrians. Hawkers on the corner offered beads and newspapers. The footbridge, a couple hundred meters ahead, arced up over to the U.S. border beside the bridge for cars, jammed and barely moving. Without me onboard my host could avoid this line, using his express pass to meet me on the other side. By walking four hundred meters I saved us each an hour or more. It was an easy trade.

That border changed my travel strategy, led me to the single backpack packing method I use everywhere now. It also taught me that the strangest feeling a border can bring is that of having to ask to be let back in to one’s own country.

So much easier, less stressful, and faster, to ask for permission to enter Hong Kong.

The walking borders of my life two years ago were all between Mexico and the U.S. Mostly El Paso and Juarez, but also Tijuana and San Diego, after long days on the road. Those trips, a staple of my 2012 existence, have disappeared from my life entirely, replaced by Shenzhen and Zhongshan, by so many evenings in Hong Kong. In some ways it’s a direct exchange. I have traded the hot summer afternoons in Mexico, the air dry, for Hong Kong’s humidity and Dongguan’s pollution. Walking back from where the car traffic became impenetrable, almost a mile from the border in Tijuana, to my rental car on the other side of the US border, heading to San Diego airport, flying back to SFO, all that has been replaced by a car ride to Lok Ma Chau, a walk across that bridge, a train ride to Yau Ma Tei, a train to HKG, a flight to SFO. Longer, but much the same. Travel necessitated by sprawling supply chains that are themselves created by the artificial borders I cross.

What would I have said, at twenty, if told that fifteen years later I’d walk the border between Shenzhen and Hong Kong a dozen times a year? Would I have been more surprised to know that at thirty three I’d spent months in Juarez? I suspect that twenty year old would be surprised by both, and then by neither, because he too was always seeking adventure, seeking to understand new things and to learn new places. He would be surprised at the specifics, at this afternoon’s offramp stroll. The general picture, of a life on the go, crossing borders on foot for money, would seem entirely appropriate. Or perhaps that’s the present talking, aware of all the strange jobs and odd decisions that brought me here. Perhaps that boy of twenty would doubt this future’s existence entirely, knowing little of Mexican factories and less of Chinese customs.

Either way, I’m glad to be back in Hong Kong, one border closer to home.