this disclosure describes a plastic container with a bottom portion , having a base , a lower stand - on - edge and an upper rim , and with a cover portion having a peripheral vertical wall which engages the upper rim of the base . parts designed to engage lockingly with one another are present on the portions in the form of projections and in the form of indentations at regular intervals about the circumference of the portions . guide surfaces are positioned about one of the portions and extend towards the locking elements of the other portion for guiding the locking elements of the portions to converge for engagement .