Brush seals are composed of thousands of fine wires and are used to form barriers against flying debris and liquid, block the infiltration of light or air, and seal gaps in doorways. They are available in many shapes and sizes and made from a variety of materials. Brush seals are useful in turbines and aerospace applications because they can form effective barriers while also allowing for thermal or mechanical movement. They are used in high temperature applications to reduce heat loss and in acoustic applications to reduce sound transfer. Brush seals are also used in hollow doors, double hollow metal doors, dock levelers, double doors, doors, rolling steel doors, sectional overhead doors, and windows.