Agree with vlpate, these twist ties are common for apartment maintenance to have.
Quick story..I had a short term lease on an apt. when I was waiting for my house. It was a quick turnover, the maintenance were actually doing my exit inspection and getting ready to clean the carpets for a new tenant the day I was moving out. The maintenance man saw me putting my kids' stuffed animals and bedding in boxes, and gave me some super duper industrial trash bags to use instead, with those similar type of ties (the ones he gave me were like the ones pictured above, but they were bright yellow.)
I know my story has nothing to do with the case, but this is how I came to learn that some apartment maintenance workers carry those ties. He had a little push cart (like a housekeep cart at a hotel with bigger wheels) with the bags, ties, and some cleaning products.
The ties just slide on easily but lock into the tightest position you pull them to, and need to be cut off to be removed (the slide is serrated and not reversible)