Spread a kitchen towel on the counter. Use your jar lifter to remove a jar from the canner. Pour out the water (save it for washing dishes), and place the jar on the towel. Keep the remaining jars in the canner, so they stay hot.
Use the canning funnel and pack the prepared string beans into the jar. Try to pack them in tightly while leaving a 1-inch headspace. If you are using canning salt, add 1/2 teaspoon per pint jar, and 1 teaspoon per quart jar.
Ladle boiling water over string beans and fill the jar maintaining the 1-inch headspace. Remove air bubbles with the bubble popper and wipe the rims.
Use the magnetic lid lifter to lift the lids out of the warm water, center each lid on the jars, and screw on the bands until fingertip tight.
Center a lid on the jar, place the band over the lid, and screw it on until fingertip tight. Using your jar lifter, immediately place the jar back on the rack in the canner, and repeat with the rest of the jars until the canner is filled, or you run out of beans.
Close the pressure canner and secure the lid. Leave the vent open, adjust the heat to medium-high, and bring the canner to a boil. Allow the pressure canner to vent for 10 minutes, then place the weight on the vent.
Bring the canner to 10 pounds of pressure, start your timer, and process pints for 20 minutes, and quarts for 25 minutes at altitudes of less than 1,000 ft. Follow the directions for your pressure canner and adjust processing time for your altitude if necessary (see note below).
When processing time is complete, turn off heat, and allow pressure canner to cool down to 0 pressure on its own. Once the canner is depressurized, let the canner cool 10 minutes before removing the lid.
When the canner is cooled down, spread a kitchen towel on the counter, unlock cover, and remove it by tilting lid away from you so that steam does not burn your face. Allow another 10 minutes for the jars to adjust to the change in pressure.
Use a jar lifter to lift jars carefully from canner and place on towel. Don't tighten bands or check the seals yet. Let the jars sit undisturbed for 12 to 24-hours to cool.
After 12 to 24-hours, check to be sure jar lids have sealed by pushing on the center. The lid should not pop up. If the lid flexes up and down when the center is pressed, it did not seal. Refrigerate the jar and use up within a few days.
Remove the ring bands, wash, label, date the jars, and store the jars in a cool, dark location (50 to 70 degrees F). Use within a year for the best quality. Yields 9 pints or 7 quarts.