Blanch beans in boiling water until tender but still crunchy, about 3 4 minutes. Drain and run under cold water immediately to halt cooking.
Place 1 one clove garlic, cayenne to taste and 1.5 sprigs dill into each of two sterilized pint jars. Pack beans upright into the jars, to fit within 36 cm of the rim. In a non-reactive saucepan, bring vinegar, water and salt to a boil; pour hot liquod into the jars leaving 1 cm head space. Seal and proces the jars in a boiling-water barth for 5 minutes.
Store for at least 2 weeks in a cool, dark place before eating. Serve cold from the refrigerator.