They have some ticks ( or tics ) on a card that says they were qualified ( on a certain date, remember amnesia ) to do some things, but maybe not all things, connected with gas.
Not sure what exactly your point is? If he's gas safe or the bloke who visited is gas safe without the relevant qualifications then neither of them should be in the combustion chamber fitting screws into heat ex's to stop leaks. Simples.
