Definition
An e-kanban setup that binds a set of parts supplied by the same vendor into one group; scanning any card in the group lets the scanning person choose to replenish just that item or the whole group.
In detail
Lock Step is an E-Kanban setup that binds a group of materials supplied by the same supplier into one group: when any item in the group is scanned, the scanner chooses whether to replenish only that item or the whole group together. It solves shortages or overproduction caused by mistimed replenishment of related materials—replenishing the entire set every time is itself another form of overproduction. Unlike individual replenishment, it emphasizes optional linkage within the group, and the output is a replenishment instruction plus the choice of "how many pieces to replenish."
Example in practice
A product requires three materials A, B, and C from the same supplier to be assembled. After setting up Lock Step replenishment, the three materials are bound as a group: when A is scanned, the scanner can choose to replenish only A, or replenish B and C together; always replenishing the full set would instead cause overproduction.