Expanding on the blog post from April 2015, there are two features unique to the Hillside Washer that allow it to function. The Locking Tab and the Spheroid Shape.
Figure 1 shows a Hillside Washer in a typical layout. As the Turnbuckle Rod is tightened it naturally creates a secondary force as indicated by the arrow. If allowed to move with that downward force it would eventually bottom out at the lower edge of the hole and the rod would begin to bend.
To prohibit this movement Hillside Washers have a Locking Tab that seats at the bottom edge of the hole. It prohibits the Hillside Washer from moving downward with the force. It is important to note the useable range of a Hillside Washer is from the mid-point of the sphere to the maximum angle of the side opposite the Locking Tab. The Turnbuckle Rod should never be situated between the mid-point of the sphere and the locking tab.
Figure 2 shows the Locking Tab resisting the force created by the Turnbuckle Rod being tensioned.
The circular shape of Hillside Washers allows the angle of the rod to vary. Regardless of the angle it always presents a perpendicular mating surface for the Washer and Nut. (Fig. 3)
Also note in Figure 3 the angle of the rod will require it to have an elongated hole. If possible the hole should be oblong, not round.