A shelf organizing system for dividing flat merchandise display shelving. An extruded front rail member typically of generally L-shaped configuration is secured to the front of a shelf, providing a vertical barrier wall. A retention channel, preferably including one or more resilient retention flanges, is formed integrally with the front rail member. Divider elements, extruded in continuous lengths and cut to desired length for particular shelf width, are formed with a vertical flange and a horizontal stabilizing flange. The stabilizing flange is insertable in the retention channel, at any point along its length, and is tightly gripped therein to hold the divider element in any desired position. The divider element may be easily installed by pressing laterally into contact with merchandise to be segregated, and then moving the divider into the retention channel. Divider elements may also be formed advantageously of wire instead of plastic. The system facilitates maintenance of neat shelf displays, which has been proven to increase sales.