Never push the cloth part of the swab into the bell because this causes it to bunch up. Then gently pull the end of the cord until you have drawn the entire swab through the clarinet. It is best not to swab the mouthpiece because doing so tends to wear it down over time and change the way it plays. When a Swab Gets Stuck It is important to make sure that the swab is completely unfolded and straightened out before pulling it through. If a swab is not entirely unfolded before pulling it through, it can easily catch and tangle on that vent tube.
Stuck swabs can be slightly frightening, and are sometimes difficult to get unstuck.
If your swab does get stuck, stop pulling immediately. The way to get it out is by taking apart the clarinet, and then very gently pulling the swab out backwards. It's best to get into the habit of always swabbing your clarinet at the end of each playing session. However, depending on the humidity, temperature, and individual player, you might need to swab the instrument occasionally during the playing session. When condensation is allowed to build up, it can result in tone holes getting clogged which causes certain notes to gurgle.