The "hold" was created in 1986 by John Dewan and Mike O'Donnell (who worked together on The Chicago Baseball Report) to measure the effectiveness of relief pitchers who rarely get a chance to close a game.
A hold is credited any time a relief pitcher enters a game in a save situation, records at least one out, and leaves the game never having relinquished the lead.
More than one reliever can earn a hold in a game, even if they protect a lead that is later lost by another reliever.
But the hold is not an official statistic in Major League Baseball. (STATS, Inc., requires a reliever to record at least one out for a hold, while SportsTicker does not.)
Mike Stanton and Jesse Orosco top the unofficial hold list in Major League history. Mike Jackson, Dan Plesac and Paul Assenmacher are some of the other top hold guys.