Each transshipment siding (sometimes referred to as a transfer dock or a wharf or a loading bank) had either one or a pair of narrow gauge lines raised on a platform meeting a standard gauge line end-to-end. The standard gauge transporter wagons (sometimes called "host" wagons) were flat wagons with narrow gauge tracks set on top. The heights of the tracks meant that six slate wagons could be manhandled 'pick-a-back' onto each transporter wagon in pairs, side by side. They were made up to trains then hauled to Blaenau Ffestiniog where either the above process was reversed with the narrow gauge wagons being manually propelled onto the narrow gauge Ffestiniog Railway or they were unloaded, sorted and transshipped into GWR standard gauge wagons. When the latter happened they ended up travelling southwards past Tan-y-Manod on the way to their final destination. The layout of at least the most northerly of the raised sidings lent itself to unloading slates conventionally, side-by-side from narrow gauge wagons to standard gauge, but use in this way is not described in sources.