Sterilize jars: Bring approximately 4 cups of water to boil in a saucepan or teapot. Carefully pour half of hot water into each jar, gently swirl (hot pad recommended) around and then discard water.
Wash carrots, trim ends and cut into sticks the length of the wide part of the mason jar (about 4 inches). Place half of carrot sticks in each mason jar, standing upwards. They should fit snugly.
Stir together water and salt. Doing this in a large measuring cup makes it easy to pour into the jars. Pour half of water into each mason jar until it reaches about 1/2 inch from the lip of the jar. The carrots should be completely submerged.
Top each jar with a lid (screw on loosely) and place on the counter in a place they won't be disturbed. Avoid direct sunlight. The ideal temperature is 60-70 degrees F.
Let sit for 5-10 days. Every 1-2 days unscrew the lids to let pressure escape. If a carrot pops up above the salt water line, simply push it back down (with a stainless steel utensil).
After 5-10 days, transfer jars to the refrigerator, including salt water. To eat, simply grab a few with a clean fork, rinse under water and enjoy!
Notes
Store in a sealed glass container in the refrigerator for up to 6 month.