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.
A roosting box is a weathertight box with an entrance hole set low and one or more perches mounted inside. Unlike birdhouses they do not have vents or drainage holes, so the warm air generated by the roosting birds is retained. Boxes can vary in size, depending on how large the number of birds you want to accommodate.