OK, assuming that's right...I was referring to the whole piece being a solid bar instead of 2 interlocking ones. So I guess the spline allows it to move up and down to absorb some impact and prevent breakage/snappage that could occur with a single solid piece?If it was a straight or smooth bar, the smaller piece would spin around inside the larger piece, and the steering wheel wouldn't grab very well. The splines help lock the two pieces together, I think, but still allows them to move up and down (but not rotate). I could be wrong. This is my uneducated opinion on the matter.