I’ve done this since I was a teenager, but don’t think I’ve passed this tip along. If the string in your hoodie or sweatpants slips inside the garment, don’t fret. Pull the string out completely. Attach a small safety pin to one end of the string (make sure it fits through the opening). Insert the pinned end back into the hole and use the safety pin as a guide to work the string through the channel. Keep smoothing the fabric along the way until the string comes out the other side.