Place the apples on a cutting board and core. Cut one apple in half. Place one apple half, flat side down, on the cutting board and cut lengthwise into quarters. Cut the quarters into 1/2-inch pieces and place in a large mixing bowl.

Repeat with the other apple half and the remaining apples.

Add the walnuts, celery, raisins, mayonnaise, lemon juice, vinegar, and salt, and stir well.

Serve immediately or cover tightly with plastic wrap and refrigerate for up to 6 hours.

Lemon juice is often added to cut-up fruit -- lemons contain a special acid, called citric acid, which prevents fruit from turning brown. The juice of other citrus fruits (like oranges and limes), as well as pineapple juice and the juice of some berries, will have the same effect.