What should the support letter say for a Thunder Bay engineer whose assignment repeats every winter?

It should describe one season at a time. The current letter states the operator's legal name, Eero's name and Canadian citizenship, the profession in the wording used by Appendix 2, the engineering tasks planned for that lay-up, the dates, the pay and who he reports to.

A recurring assignment needs a current letter, not a reusable one

The temptation with recurring work is to keep one letter and present it every year. That habit produces a document describing vessels that were overhauled two winters ago, alongside dates that have long passed. Reissue rather than annotate.

A useful version names the ships or classes involved, the engineering deliverables expected - alignment reports, repair specifications, machinery condition assessments, drawings released for the yard - and states the period being requested along with the salary and the reporting line. Attach the parchment, the transcript and the provincial licence certificate. Where an earlier season's letter was presented at a border, keep a copy, because an inconsistency discovered later is far more awkward to explain than a change that was documented at the time.

If the operator files Form I-129 instead, the same care applies to the petition's description of duties.