at my job i have an 8 hour/day contract but i only work when are available projects. this works like that: when they need people to work, i have to work 12-14-16 hours/day for 1-2-3-4 weeks and then, when there are no projects, i stay at home and get the same salary .
Cons
it is a streesfull job where all the people shout to each other
many hours/day and the food is very bad, sometimes you get a big stomacheache from that.