Abstract: A method of making an assemblage of cargo containers includes use of a self-locking swivel stacking pin tool (10) with an elongated handle (12) having a handgrip (18) at a hand end thereof and a pin-housing engaging member (20) at a pin end thereof. A locking-head actuator (14) having an elongated force-transmittal portion (46) slidably extends along an elongated shaft (16) of the elongated handle, with a trigger (48) at a hand end thereof and a locking-head rotator (50) at a pin end thereof for engaging a bottom swivel locking head (38). By moving the trigger relative to the handgrip an operator can cause a rotatable axle (40) of a swivel stacking pin to rotate and thereby cause a top swivel locking head (36) to rotate and align with a top housing insert section (28) so that the top swivel locking head and the top housing insert section can be inserted into a hole (13a) of a second cargo container (13) by manipulation of the swivel stacking pin tool.