Earlier quoted context omitted.
Never do anything by yourself which requires a permit (HVAC, Plumbing/Gas, Electrical), unless w.r.t. electrical it's low voltage boxes covered by standard switchplates with the breaker box off. Never do anything structural/load-bearing. Avoid touching window-headers/columns, door-headers/columns, that random beam in the middle of your living room, that random pillar that you wish you know what was for, and that real…
Pretty sick of this, really. I know it's meant to stop idiots from doing work that could endanger them and others, but I've serviced my own boilers, installed my own sockets for years and even laid out the electrical for a whole house. Now some dickwad comes and tells me "man, that is illegal". k
That is _not_ the person I want working on a gas line (which is "plubming") on a house I'm going to buy in the future.
I'm sure you're a special little snowflake that's good at everything, but if you don't feel comfortable getting a permit for permit / license-required work, then... um... maybe you shouldn't be doing it? That's the context for the advice I gave to the parent poster.