Liz,
Ignore not a Psychic, that person seems to get more joy from telling people how daft they are than actually helping.
Firstly, as CDC says, the fact that your repair people don't know is a concern. If however, you had a friend do this and they genuinely don't know, then get them to take CDC's advice and Google it.
Help the contributors by giving as much detail as possible.
Oldgrubber, April 2017