A boundary marker is like a sign or a signal that tells us where one thing ends and another thing begins. Think of it like your bedroom. You have your bed, your toys, and everything you own in your bedroom. But outside your bedroom, you have the living room, the kitchen, and your parents' bedroom. Your parents may have told you that your bedroom is your space and not to go into their bedroom without permission. But how do you know where your space ends and their space begins? That's where a boundary marker can help. Maybe there is a line on the floor or a sign that tells you where your bedroom ends and their bedroom begins. That's a boundary marker. It helps you know where you're allowed to go and where you need to stop. The same thing can happen outside when you have a yard. Your yard is your space, but maybe your neighbors have a yard too. A fence, a hedge, or a line of rocks can be a boundary marker that tells you where your yard ends and where your neighbor's yard begins. It helps keep things clear and fair for everyone.