A gantry is an object that extends horizontally from a mast, and is applicable for portals and TTC structures.

Each gantry has one or more sub-objects called ‘Offset(s)’, these are used to define and attach the gantry to all applicable masts.

An offset contains the attachment relationship between the gantry and a mast, any graphics for the attachment and any allocation data for the attachment between the gantry and the mast.

Multiple offsets are required when the gantry has a different method of attachment, graphics, or allocation.

If the gantry has multiple methods of attachment to the same mast, then a new gantry must be created for each method of attachment.