This is the 18.125" long bracket for the rear of the leg/motor. It goes lengthwise with the desk, and is connected to the connecting bracket to give the desk stability. This (latest) version adds a small fillet on the inside corner along the length of the bracket. All holes should line up perfectly.

This bracket measures 1.09" x 1.09", but is most likely just regular 1x1" angle iron. It's made from 1/8" thick steel.

The 4 larger holes are 0.34" diameter.
The 5 smaller holes are 0.225" diameter.

The 4 large holes are at 0.4" from the left edge, 5.93", 12.195, 17.725"
The 5 small holes are at 0.4" from the left edge, 4.73125", 9.0625" (midline), 13.39375", 17.725"