Things you'll need:
Wooden bench (any wooden obstacle that you want will work)
Knife
Willingness to risk messing up your obstacle
Step one: Take your knife and cut slits in your wooden bench like this
Step 2: Keep cutting out slits until you reach the end of your obstacle.
Tip: The deeper the cut the louder the sound.
Step 3:Cut a long line at the top to form the bricks.
Optional: At the bottom of the slits, cut a long line to completely form the bricks.
Here's what it should look like in the end: