Self-centering features for stackable containers

A blank for a container comprising:

• a plurality of panels for forming a polygonal section comprising lateral walls surrounding an interior space;
• a plurality of upper flaps foldably connected to respective ones of the lateral walls along respective upper fold lines and configured to form an upper wall forming at a top bound on the interior space;
• a plurality of lower flaps foldably connected to respective ones of the lateral walls along respective lower fold lines and configured to form a lower wall at a bottom bound on the interior space;
• an alignment tab that straddles a first one of the upper fold lines, wherein a first end of the alignment tab is connected to the first upper flap by a first join line and a second end of the alignment tab is connected to an adjacent one of the lateral walls by a second join line, wherein the alignment tab has two opposed lateral sides crossing the respective one of the upper fold lines, wherein the alignment tab also has an intermediate fold line between the first and second ends of the alignment tab that is closer to the first end than to the second end, such that the alignment tab is configured to project upward from the upper wall and to separate two vertical, inward facing alignment edges at an upper end of the adjacent one of the lateral walls, and
• a retention tab extending downward from the adjacent one of the lateral walls across one of the lower old lines, wherein the retention tab is configured to engage two vertical, inward facing alignment edges of a similar container for alignment in a stack.