Step 4: The X axis - Horizontal Axis (step #1)
This U shaped part (the X axis carriage) will hold the Y axis stud.
Here is the Home Depot Catalog number for the part below:
"Half Base" made by Company named Simpson
Catalog number : C751-973
Home Depot num: 044315-10350
these parts were punched and then bent, when we decided to make our own parts we had
them laser cut and bent - then powder coated