Wash cucumbers, removing blossom ends.
Remove stem or leave 1/4" inch of stem intact. Cut in half lengthwise.
Heat vinegar, water, and salt to boiling.
In each jar, put 2 heads dill or 1-2 tsp. dill seed, 4 halved garlic cloves, and 1 tsp. black peppercorns (if using).
Pour hot vinegar solution over cucumbers, leaving 1/2" headspace.
Fill water bath canner halfway with water. Place the canner on your largest burner, and turn on the heat so the water is very hot but not boiling. Place your filled jars into the canner's rack.
Lower the rack with the filled jars into the canner. Add simmering water if needed to cover the jars by 1 to 2 inches. Turn the heat to medium-high, place the lid on the canner, and bring the water to a full rolling boil.
Process quarts for 15 minutes at 0 to 1,000 feet elevation; 20 minutes at 1,001 to 6,000 feet elevation; 25 minutes above 6,000 feet.