I have had black snakes in my yard and in my garage since I moved here eight years ago. The two in the garage I simply chased out with a broom. One of the snakes in the yard was a big boy who struck at me several times and disappeared into a bush where I couldn't see him to shoo him out. After that, I got rid of all of the bushes and made "snake guard" that completely covers the bottom of my courtyard gate, and I haven't seen another snake since them. To get in my courtyard they will now have to climb a six foot wall, and while they are capable of it, I think they just go elsewhere.

Duh!!
 

Put up a sign..."No snakes allowed"

Friendly black snakes
 

One got in our garage and left on its own. One got in the birdcage. I just gently “encouraged” it with a broom toward the door to our yard. They are as in the category of many insects as “beneficials”.

That will work!