This invention relates to the field of containers such as used for packaging retail products and has particular adaptability in the field of disposable containers for packaging fast food items and the like. 
The prior art has employed a variety of containers for various purposes.  One area of particular concern with the prior art is the provision of suitable locking mechanisms.  It is known in the prior art, for example, to utilize a straight tongue-slot arrangements such as disclosed in U.S. Pat.  No.  3,968,921.  Another arrangement disclosed in U.S. Pat.  No.  3,876,130 utilizes a flange-in-slot recess type.  A still further arrangement disclosed in commonly assigned copending application Ser.  No.  769,567, filed Feb. 17, 1977 incorporates a dual tongue for fitting in a pair of slots.