An unconventional Wall Street financing tool is increasing in popularity. Investors should make sure they aren’t on the wrong side of the cash machine.

Hertz Global Holdings, which has filed for chapter 11 bankruptcy protection, on 15 June said it plans to sell as much as $500m in stock through an at-the-market financing. In this type of deal, Hertz can instruct its banker to sell stock on a rolling basis at prevailing market prices. That differs from a traditional offering, where an investment bank will sell shares to blocks of institutional investors in one shot at a fixed price.