Summarize the following:
Cut into slices approximately inch in diameter. If you prefer you may use thinner or thicker slices. The cucumber and summer squash should be about the same thickness. You can pickle in food grade plastic, stainless steel or glass. Aluminum and copper are not suitable for pickling. Bring to a boil. Cool.
Wash the cucumber and summer squash. Peel cucumbers and summer squash. Place cucumbers, summer squash and sweet onions in a bowl. Combine vinegar, sugar, salt, celery seed and mustard seed in a small saucepan. Cook and stir just until sugar is dissolved. Pour mixture over cucumbers. Cover tightly and refrigerate for at least 24 hours.