Install a stake at either end of the garden row or bed. Place the stakes in the space between rows. Use stakes that are taller than the plants you are protecting.
Cut a 4-inch length of fiberglass strapping tape. Form a loop with the strapping tape, and stick the ends of the loop to one end of the mylar bird tape, using the strapping tape's adhesive.
Pass a length of garden twine through the strapping tape loop. Tie the twine around one stake, 3 inches down from the top.
Attach a strapping tape loop to the other end of the bird tape. Twist the bird tape four or five times before tying it to the opposite stake with garden twine. Stretch the tape so it sits above the plant tops, but still sags slightly so it can move in the breeze. The flashing of the holographic bird tape in the wind scares away the cardinals.
Install stakes and bird tape between every row of plants or bushes. The cardinals primarily feed from the spaces between the plants, so these are the areas you must frighten them from.