Standard D Ring
Most shades you see are made with the standard D Ring as pictured here.
D Ring Thimble plus Bow Shackle
This upgraded version of the standard D Ring is the the top of the line corner choice for any shade sail. Thimbled corners keep the cable in place and decreases your chances of a cable kink, which could later on break.
Although this does come at an extra cost, included in that cost is the corresponding shackle used to connect your sail corner to the turnbuckle.