Depending on which species of black snake you are catching, there are a few different methods to try. Many snakes that are commonly referred to as "black snakes" are large, sometimes able to grow 5 to 8 feet long. Not many of the venomous snakes of the United States are black, and those that are have other markings on the predominately black body. Rat snakes, racers and bull snakes are common large black snakes. Glue traps may be the best method of trapping any snake, and they are among the most humane.
Damp Cloth Method
Place a pile of crumpled damp cloths or towels on the floor. Place dry cloths over them to keep the moisture in the crumpled damp cloths. Snakes that have made their way inside will enjoy the damp retreat.
Watch the pile for the snake to enter or check it periodically.
Remove the pile of cloths, snake and all, and take it outside to allow the snake to retreat on its own.
Glue Trap Method
Place a snake trap or glue boards along the perimeter of the area where you have seen the snake. Several brand names of snake traps are available at hardware stores and online. Typically, the trap is a cardboard box with adhesive on the inside. Don't expose the trap to the elements.
Check the trap several times a day. Leaving a snake on the glue board or in the snake trap box is inhumane.
Identify that you have captured a nonvenomous snake. Besides coral snakes, all venomous snakes in the United States are pit vipers. Pit vipers have a pit between their eye and nostril and vertical, cat-like pupils.
Take the snake, still inside the trap, to a suitable habitat far away from your home or building; a mile is more than sufficient.
Apply vegetable oil to the snake where the glue is. If you are afraid of the snake, you can pour vegetable oil on the snake. The vegetable oil releases the adhesive within a few minutes to an hour.