This riddle asks: what do you throw out when you want to use it, but take in when you don’t? The wording sounds backwards, which is exactly what makes it tricky.
The answer is an anchor. When a boat needs to stay in one place, the anchor is thrown out into the water so it can catch on the bottom and hold the boat steady. When the boat is ready to move again, the anchor is pulled back in.
So the object is thrown out when it is needed and taken in when it is not. The riddle works because “throw out” usually makes us think of getting rid of something, but here it simply means lowering an anchor from a boat.
