Abstract: An interlocking arrangement for plastic containers is disclosed, which is particularly suitable for use in a container system for storing and dispensing film-processing chemicals. The interlock arrangement comprises two sections, a curved protrusion, and a tapered flange, the protrusion being located near one end of the flange. The interlock, which has both male and female portions, is integrally formed with the plastic container with which it is associated. The interlock tends to prevent containers from accidentally separating during transportation and handling.