An IBKR program for Portfolio Margin clients. Once you have registered, this program lets you pre-borrow stocks in anticipation of a short sale using the Stock Borrow/Loan page in TWS. Pre-borrowing can help to avoid a buy-in by ensuring that shares are available to short before you put on the short sale. Without a pre-borrow, you will not know for certain if shares have been procured until the short sale settles on T+3.