In the first half of March, three banks - Silicon Valley Bank, Signature Bank, and Silvergate - all had relatively classic bank runs and collapsed. Which sparked some major banking stress. As a result, the Federal Reserve got a lot of requests to use one of its oldest and most important tools for soothing such troubles: the discount window.The discount window is like a safety net for banks. And recently, a lot of banks have needed it. So, what is the discount window, where did it come from, and how does it work? And, amidst all the recent banking turmoil, has it been working the way it should? In this episode, we crack open the discount window.This episode was produced by Emma Peaslee with help from Willa Rubin. It was engineered by Katherine Silva. It was fact-checked by Sierra Juarez and edited by Sally Helm. Jess Jiang is our acting executive producer.Help support Planet Money and get bonus episodes by subscribing to Planet Money+ in Apple Podcasts or at plus.npr.org/planetmoney.