Wash and soak your mason jars and lids in hot, soapy water to disinfect them. Rinse the jars and lids with warm water. Dry the metal band lids and leave them out at room temperature.
Fill a large sauce pot with hot water. Place the glass mason jars in the hot water to keep them warm, Fill a small sauce pan with water. Bring the water to a simmer. Place the flat lids in the water to simmer until ready for use.
Wash your vegetables to remove dirt particles and pesticides. Chop the vegetables to a desired size. Keep your vegetables raw or cook them.
Bring a small pot of water to a boil.
Attach the food funnel to the top of a mason jar. Pour your vegetables into the funnel, transferring them one jar at a time through the funnel. Add boiling water to each jar through the funnel or by ladle. Leave 1/2 to 1 inch of head space at the top of each jar to prevent overflowing.
Center the flat metal lid on the top of the mason jars, covering the jars' openings. Screw the circular metal bands clockwise around the flat lids to tighten and hold them in place. Wipe off any excess food from the exterior of the jar with a towel so that the jar is clean.
Open your pressure canner. Add 3 inches of water. Bring the water to a simmer over medium-heat. Place your vegetable-filled mason jars inside the pressure canner. Refer to the pressure canner manual and your recipe to calculate the time and pressure necessary for the amount of vegetables, types of canner you are using and altitude. For example, nine pints of tomatoes require 15 minutes at 11 lbs. pressure on a dial gauge type of canner vs. 15 minutes at 10 lbs. pressure on a weight-gauge types of canner.
Lock the top of the pressure canner so it is sealed, allowing no pressure to escape. Make sure the steam vent is open. Raise the heat to a medium-high setting. Refer to the pressure canner manual to calculate the time and pressure necessary for the amount of vegetables you have.
Keep the vent pipe on the pressure canner open. Look for a flow of steam releasing through the vent. Allow the steam to release for ten minutes. Close the vent and change the heat by using the pressure canner's recommended method and calculations noted in the manual. The canner instructions may require you to implement a weighted gauge to close the vent pipe area of the canner.
Process the jars for the amount of time required according to the pressure canner's directions and manual. Remove the pressure canner from heat. Allow the pressure gauge to return to zero. Let the jars cool inside the pressure canner without interference for 30 to 40 minutes.
Lay a soft towel on a flat surface such as a counter-top. Unlock the pressure canner lid. Use the jar lifter to remove each mason jar from the pressure canner. Place the mason jars on the towel. Allow the jars to sit for 12 to 24 hours before moving them.
Press your finger into the middle of the flat lid to check the seal. Take off the metal band and try to lift the flat lid off with your fingers. The seal is good if it does not dent or pop up when you apply pressure to it and if it is not removable when you try to lift it up.