Railroad expression for uncoupling rail cars from one another. To lift or "pull" the actual pin used to lock the coupler knuckle of one rail car to another. This is done by pulling on a long round "bar" connected to the actual "pin" and can be done in the comparative safety of the area outside the rail cars being uncoupled. Early railroaders had to do this while in between the two cars being uncoupled.
Go and pull the pin between the two ACFX reefers. The hind one will be spotted at door 3