Coarsely grate the carrots and daikon into strips, or use a knife to cut into matchsticks. Sprinkle on the salt and toss to mix and let stand for 20 to 30 minutes
Meanwhile, in a nonreactive saucepan, combine the water, vinegar, and sugar and bring to a boil. Remove from the heat; cool to room temperature. (Don't cook the vegetables, bathe them). Rinse the vegetables briefly with cold water, then squeeze dry and transfer to a medium bowl
Pour over the vinegar mixture and stir gently with a wooden spoon to ensure all the vegetables are well moistened. When it has cooled down, keep it in the refrigerator. Let stand for 24 hours before serving. It tastes best at 48 hours I think, but I find it acceptable starting at 24 hours point if you are pressed for time. They can be kept in a refrigerator for up to 2 weeks