Allocated fixed costs, often called common costs, are costs that are not traceable to a particular product, service, product line, or segment. They are never relevant because the costs are assigned to a number of products.llocated fixed costs, often called common costs, are costs that are not traceable to a particular product, service, product line, or segment. They are never relevant because the costs are assigned to a number of products.
Definition of roost. 1  1a : a support on which birds restb : a place where winged animals and especially birds customarily roost. 2  2 : a group of birds roosting together.
One of the great animal phenomena of the world is the congregation of large numbers of birds into a single group to sleep together. Such communal sleeping groups are known as roosts.. Many species roost in groups; such things as crows, robins, starlings, blackbirds, swallows, and herons. Another idea is that the birds get some protection from predators by being in a large group. 2  This is the wagontrain analogy: safety in numbers. 3  Crows are most afraid of large owls, and sleeping with a bunch of other crows could afford some protection for an individual crow.