Prepare beets as for Buttered Beets. Cut them in slices and lay them in a stone or glass jar. Allow one slice of onion for each beet, one tablespoon grated horseradish, eight cloves and vinegar enough to cover. Let stand twenty-four hours and they will be ready for use. Beets thus prepared will not keep longer than a week. If vinegar is too strong, dilute with one-fourth part cold water.