The smart way?

[scoutingranch]

I am sure I didn't write it by the correct name. It's the splined end the wiper arm slides on to. I don't want to ruin it if there are none available. Thanks

[bmorgil]

That just looks strange. There is a splined shaft on the motor the wiper arm slides on and then there is a Brass Acorn Nut that secures the arm. It almost looks like the original nut is completely rounded off, or there is part of the old wiper arm stuck on the shaft.