What wires conductors would go under x lug in a transformer?

The primary side of a transformer is identified as the H side, eg. H1,H2,H3,H4. The secondary side of a transformer is identified as the X side. Eg. X1, X2. Usually X1 goes to a fuse and then to the load, X2 is usually the neutral side and is grounded to the body of the transformer.