Used As Lifting Bridle Connection Points
Extra holes in the side stay tangs are used to connect the two forward wires/ropes of a lifting bridle. The third connection point is on the cockpit floor towards the transom.
The side stay adjusters in the photos above show adjusters with a series of holes for adjustments. Virtually all boats use these on their upper side stays; many also use them on their lowers. However, a number of racing skippers now use the turnbuckle style shown at left on their lowers to give more precise adjustments (these are branded “Sta-Master“).