Also called a shelf registration, this allows an issuer to sell a variety of securities (debt, equity, warrants) at any time over a two to three year period, provided that they meet certain criteria. When issuers decide to take securities off the shelf and sell them ("takedown"), they can use an underwriter or other selling agent, or sell directly to investors. Despite their greater flexibility and lower costs, shelf offerings are far less common than follow-on offerings. Investors value the due diligence provided by banks in an underwritten offering. Meanwhile, the uncertainty of having registered shares sitting on the shelf creates an overhang that many investors avoid.