Resources may be drawn from one or several queues so that the properties of those drawn from one queue match those drawn from the other queue(s). In the worst case, matching fails. This situation typifies matching problems. For example, a water boiler has a designated location in a house under construction; when the boiler is ready to be installed, workers must have access to that designated location to work; no other location will do. Another example is to install only complete pipe runs (Howell and Ballard 1996) or to load various structural steel shapes onto flatbed trucks not to exceed the truck's dimensions or load capacity (Martinez 1996).