Hi, all. New here. Currently I'm a computer science student so I have some background in physics. I do not know very much about mechanical/structural physics or the equations associated with them. Currently, I am trying to build a small utility trailer and have questions about the steel tubing size that is appropriate for the load I would like to carry. I have downloaded some beam structure software, which calculates shear and the maximum bending moment. I do have some questions on how to interprete the graphs associated with shear and max bend moment. If anyone can direct me to a tutorial or simply explain these graphs and what they mean I would appreciate it (vert and diag lines intersecting the x axis). I also need some info on how to determine what size and guage steel to use. I know what my max load is that I want the trailer to carry (and have an idea of the size of the tube) but I am having a hard time figuring out how to determine what guage steel to use. I could go with oversized steel but I really do not want to overbuild it as weight issues might become a problem. Any help would be greatly appreciated.