Securities Lending

See: Margin.

When you create a margin account at your brokerage, you are essentially using your own securities as collateral for the purposes of "lending them" against incremental purchases.

Like...you have $10 million in MSFT stock. You can lend those securities "to yourself" to generate $5 million more in buying power with a 50% margin limit. Common practice. Risky, if the market goes down. And you'll pay the brokerage a few percent in margin fees for their acting as intermediary in that securities lending experience.

So...here's to bull markets.