Management and workers at a Port Adelaide hardware store have been locked out because of a rental dispute with the landlord.
The Construction, Mining, Forestry and Energy Union (CFMEU) says the Mann's Mitre 10 has been closed until further notice.
The union says a notice on the door of the Robe Street business alleges the tenant has failed to pay $315,000 in rent from September.
About 50 workers were told last night not to turn up and the union says the future of the business is now uncertain.
CFMEU state secretary Dave Kirner says the closure means workers are missing out on pay.
"My understanding is that pays are done through the site itself," he said.
"It's a 90-year-old Port Adelaide institution and obviously tradespeople have gone there this morning to get organised to get things for their jobs and the place is all locked up.
"The lawyers have apparently moved in and changed the locks on the building.
"In the back of people's minds is this issue about whether the place is going to continue operating or not.
"Normally in these situations, somebody comes in and actually people get some information and understandings.
At this stage people are really in the dark."