Find the diameter of the tie rail and halve and then subtract half the thickness of the tie rail support. Mark this measurement in from the outside edge of the chassis rail and use a string/chalk line to mark the full length of the chassis rail. This will be mark for lining the tie rail supports up to.
Align the front tie rail support top leading edge, 55mm back from the front of the chassis crossmember and all other supports 520mm apart along the length of the chassis rail.
Use a straight edge on the side of the chassis rail to butt the tie rail up to and tack weld the tie rail to the supports.
Fit the 90 deg bend and repeat the tie rail fitting to the front of the trailer using the 45 bend and tie rail stub to finish.