Begin by washing the jalapenos well. I highly recommend that you were latex gloves for this next part.
Slice the jalapenos into ¼ inch slices, discarding the stem end.
Pile the jalapenos into the clean, hot jars. Set aside.
Next, measure the vinegar, water, and salt into a saucepan.
Over medium heat, bring the mixture to a boil. Stir until the salt has fully dissolved.
Ladle the brine into the jars. Remove any air bubbles.
Top up the brine, being sure to leave ½-inch headspace.
Wipe the rim of the jar with a clean, moist paper towel.
Place the lid on the jar and process in a prepared waterbath canner for 10 minutes.
Remove the jars from the canner and allow them to rest for 24 hours on a wire cooling rack which has been covered with a tea towel.
Once cooled, wash the jars in soapy water and dry them.
Label and store in a cool, dark pantry.