Our season extension kits include: galvanized wire hoops (10 gauge, 74" long), row cover (provides 4 degrees of frost protection), wooden clothespins (yes! they do the trick!).
We use row cover throughout the season for a variety of reasons. It works wonders to protect young plants in the early spring against wind, big fluctuations in temperature and heavy rain. We also use them to harden off seedlings. In late spring and summer we use the covers on brassicas (like kale, broccoli, et.) to keep out insects like cabbage worms. In the fall, we use the covers to protect our tomatoes, peppers, eggplants, and basil to last through the early frosts and well into October.