A container assembly comprises a first container and a second container. The first container includes a first continuous body portion and a first rim. The rim has a first plurality of ribs projecting generally upwardly therefrom such that first spaces are formed between adjacent ribs. The second container includes a second continuous body portion and a second rim. The rim has a second plurality of ribs projecting generally upwardly therefrom such that second spaces are formed between adjacent ribs. The second rim and the first rim are shaped substantially the same. The first container and the second container are adapted to be releasably lockable to each other by fitting the first plurality of upwardly-projecting ribs into respective second spaces and fitting the second plurality of upwardly-projecting ribs into respective first spaces. The first container may be shaped substantially the same as the second container.