We used an old window to cover a portion of the bed, protecting lettuce starts from the cold and wind, and hungry birds.
Up close, you can see the difference it makes, as the one that’s fully exposed doesn’t compare to the healthy head of lettuce that’s shielded.
Dale Dougherty 
Oops, that’s from me, Patti. 🙂
Dale, are you using emitters, or is it a soaker hose?