That Hole-in-the-Wall is literally a hole in the wall. If you look at the satellite photo of that area, you'll see two revetment walls going up the Detroit River meant exclusively for commercial shipping. However, there is a break in that wall so recreational boats can cross from one side of the river to the other. Hence, the "Hole-in-the-Wall", located right on the US/Canada international border. I'm not sure the hole is hiring though.
Oops...hit the post button too early. The hole that is actually hiring is in California's Mojave National Preserve. There's even an "Information Center" on the hole. Here's the map.