to craft a triple cast lobster

Means having sex in the workshop, you tell this to your relatives if you want them to think of you as an innocent craftsman. You hope they are too impressed to ask any further.

Aunt: "So, what were you and your partners name doing in the workshop last night?"
You: "Oh, we went over there to craft a triple cast lobster. It was pretty intense, but we made it!"
Aunt: "Wow, sounds impressive... Anyways..."