Vertical locking system for shipping containers

Means for the releasable vertical securing of stacked shipping containers at their standard corner fittings, particularly in hard to reach areas in a block of containers, is provided by a unitary passive vertical connector having an extended planar base member with a canted post rising out of one extended surface and a flanged foot depending from the opposite extended surface. When the flanged foot is trappedly engaged in a corner-fitting recess of a first container, the canted post is steerably guidable into removable capture in a corner-fitting recess of the second container. A ramp surface, which can be a part of the canted post, interacts with a corner fitting as an upper container of a pair of containers gravitates into stacked relationship with a lower container, thereby generating a horizontal component of relative motion between the containers to steerably guide the canted post. The vertical connector can include means for forming a horizontal coupling with a substantially identical connector.