International Workers’ Memorial Day

International Workers’ Memorial Day is a day of remembrance and action for workers killed, disabled, injured, or made unwell by their work.

It is an official flag flying day only in Scotland, not in the rest of the UK.

The saltire(s) should be hoisted right up and then lowered to half-mast for the day.

https://www.gov.scot/publications/flag-flying-on-government-buildings/