It happens to all parents at some point. Your child loses an item of clothing at school or an activity, and next thing you know, you're digging through lost and found. If it's not in lost and found or if you find two identical items, it will help you out if you have written your child's name in his clothing. With a name written inside, you can easily identify the item as yours or ask other parents to check for your child's name in items that wound up at their house.
Locate the inside label of the piece of clothing.
Write your child's name on the label with the fabric pen. Keep the writing away from any washing instructions if you need to know them for future use.
Write his name with a permanent marker or some other permanent-liquid-based product if you do not have a fabric pen at your disposal. One product that sometimes works well is fingernail polish.