I don’t.
Well, it depends. There’s airport security, and there’s border security. That’s two different things. When you fly from Canada to the U.S., you go through first one, then the other.
An example. The house on the right is in Canada. The road and land on the other side of the yellow curb is in the US. Neat.
Even better, check out Zero Avenue across Boundary Bay. As near as I can figure out, the border is the ditch on the right-hand side of this view of the road.
Chiming in here to say that it’s true. The Canadian officers were very kind, the American ones weren’t. I got a five minute grilling as to why I was coming BACK to the States. The Canadian officers were like “Oh, hello. Welcome to Canada? You’re here to visit? That’s nice. How long will you be here, no illegal stuff…”
That’s my experience, too. The American customs officers all seemed displeased. The Canadians were cheerful, especially when they discovered I was a Texan. “Wow! Well, welcome to Canada! Have a good day!” My own countrymen never seemed happy to see me come home. 
cross - 10 miles down through farmers field - who cares - ise a quad - horse or go camping
Old anecdote from the mid 80s when things were a bit more relaxed.
We were in Niagara Falls (US) for a League of American Wheelmen bicycle rally with somewhere around 2000 riders. There were various rides all over the US side and a couple across the border. The big scheduled ride had us loading up our jersey pockets (for non-bikers, these are sewn low in the back of the jersey) with bananas, apples, oranges, etc… for a route into Canada, their Niagara Falls park, and back out to the US. No sweat on the ‘welcome to Canada’ part but coming back was a different story. Seems our fruit (not eaten) was a problem. I was in a line of bicyclists waiting for our Q&A session noticing a large pile of fruit building up on a desk. A supervisor (I assume) came over to the inspectors for a quick conference and the questions changed to, "Are you a US citizen? Are you with the bicycle rally? and with a big smiley - Would you like some fruit? Someone had a touch of humor that day.
It depends. When visiting Canada for leisure, they are pleasant. But when visiting for business, they were among the nastiest I’ve encountered. The Americans were always gruff and businesslike.
After the travel restrictions got really hardcore, I was flying from Saskatoon to Edmonton and I followed everything to the letter - all my toiletries in the ziploc baggie, made sure to finish my bottle of pop before, etc.
I’m pretty sure they thought it was the funniest thing ever. This girl from Saskatoon all prepped like she was flying from the Middle East to New York.
The wilderness area of the border is patrolled, but not heavily. It’s just too difficult and expensive. As in many rural areas, the locals know each other pretty well and they do indeed pick up the phone when they see unusual activity, or people they don’t recognize.
If the strangers are carrying Timmie’s bags, the locals demand a cut as passage. 
The mosquitoes, black flies and bears run back-up patrols too. 