There are many areas where lettering needs to be carved directly into the structure of the boat. such as registry identification, which is required to be carved into deck beams. I have in the past carried out such work when the vessel is in a boatyard, or at her mooring. (working off floating pontoons along side is interesting, but not impossible).
Here are a few examples of past commissions:
Small ship registry numbers,
IMO identification numbers
The vessels name carved into her wheel, or her name carved directly into the hull.