Framework - Simply bolted on, with brackets, to the legs of the Up-Staging, it stands 18" (45cm) above the existing staging.
Surface - select either aluminium trays or 2¼" (6cm) wide aluminium slats.
Purchase it to run the whole length of your staging or just add an extra tier to part of it -enough brackets will be supplied to allow this extra tier extension to be fixed at either end or anywhere along its length.
To fit along the whole length of your Up-Staging, purchase your Extra Tier to the same length as your chosen greenhouse up staging.
To fit on just part of your Up-Staging purchase any length smaller than your chosen staging.