Steel doors are made in several ways. The simplest, least expensive includes a single sheet or panel of steel that forms the door. These doors also tend to be flimsier than their more solid counterparts. The other types of steel doors are made with a front and back panel for greater rigidity. An option with these doors is the availability of insulation that can be installed between the two door skins. The steel used to make garage doors comes in several thicknesses referred to as “gauge thickness” and ranges from 20 to 28 gauge. The smaller the number, the thicker the steel which means a 24 gauge door has thicker skins than a door with 28 gauge steel. When you shop for garage doors you might see reference to the quantity of “layers” with regard to a door’s construction. For example, a 4-layer door might consist of a composite overlay on top of a steel front panel. The back is made up of another steel panel and in between is an insulated core. Similarly, a door with a steel front, polystyrene insulation and no back panel would have 2-layer construction.