Glasgow Shop’s Apostrophic Grammar!

BAD GRAMMAR IN PUBLIC NOTICES IS GETTING WORSE WHEN THE NOTICES ARE HANDWRITTEN. However, the problem is not merely confined to the handwritten; look at the shop front is the picture (click to enlarge).

This is an employment agency’s shop front. The entire window is an advertisement billboard, they are seeking (sic):-

• Joiner’s
• Plumber’s
• Electrician’s
• Labourer’s
• Cleaner’s
• Lineworker’s

This is a bizarre example of misuse of the apostrophe. One would think that someone would have told them by now, but it has been like this for ages. Perhaps people do not realise the problem.
Things are getting worse.