Even though the plow in patent number 2,627,798 (‘798) is similar to the plow in patent number 2,493,811 (‘811), I would consider the ‘798 patent to be non-obvious. First of all, the ‘811 patent has a lever that controls the height of the ground working devices (plow teeth), and the ‘798 patent has no such device. While both patents have an I-beam that connects all the plow teeth together, the ‘798 patent secures the I-beam much better than the ‘811 patent. The ‘798 patent has a hook member on the mounting that hooks onto the upper flange of the I-beam and secures all the parts together. The ‘811 patent does not include this feature at all. By more securely attaching the I-beam to the mounting, the device was able to keep the plow teeth moving more uniformly without wobbling to the left or right as much while allowing individual teeth to overcome obstructions without breaking. The teeth overcame obstructions by pivoting upward and going over the obstruction instead of being allowed to move to the left or right of the obstruction and possibly into another obstruction that could cause a break. These differences took thought and innovation beyond ordinary skill, which makes the ‘798 patent non-obvious.