Holding Out

Offering transportation to the public, or to a segment of it, as willing to carry anyone who wants the service. Holding out is the element that turns carriage for hire into common carriage. Advertising and signs are the most direct way to hold out, but agents who sell seats, or a reputation for serving all comers, can do it too, and it makes no difference whether the offer attracts any business. Carriage for hire for a few selected customers, without holding out, is private carriage.

Source: summarized from AC 120-12A, Private Carriage Versus Common Carriage of Persons or Property.