Steel angle iron can be ordered to size and is sold at metal or welding shops. Special assistance with this project was provided by Boston Welding. In the workshop, Tom shared some basic rules for cutting and notching joists and rafters. For cutting holes, a hole can be no more than ⅓ the depth of the structure and cannot be within 2" of an edge. For notches, the maximum notch depth is ½ the depth of the structure and no notches can be made in the middle ⅓ of the span.