An SEC rule stating that a short sale of a round lot has to be made at a price that was an advance over the last different regular-way sale of that security. For example, if the last transaction was at 40, the next short sale must be at 40'. l/8 or higher. If the last sale was itself an advance, then a sale at the same price is a zero-plus tick and legitimate for a short sale. For example, if the last two transactions were at 40 and 40 1/8, then the next sale could be at 40 1/8-a zero-plus tick.