What you're talking about is typically casual workers. They work up to 90 days on a particular contract in a calendar year.
I can think of an instance in Gagetown. They had a whole group of maybe 30 of these casual workers who were having their names placed on boards. If anybody used any leave or didn't come in for a certain day, they would literally erase their name on the board and put it at the bottom so that they would know that they would be the last to be called in. It was a very mean-spirited way of managing people.