To create the notch for the steel to go into, you’ll want to cut the thickness of you steel out on the top of the block. Since the thickness of my steel is a 1/4 inch…yep, I cut a 1/4 inch out. I left a 1/4 inch lip at the end that will add strength to the screws. I used a bandsaw, as you can see, but you can use any other method to cut it.