Standard perforated hardboard is made of wood fibers, usually with the addition of resin, and tempered by coating with a thin layer of linseed oil and baking at a high temperature to polymerize the oil. This provides more water and impact resistance, hardness, rigidity and tensile strength. Hardboard will bend and warp with age and in the presence of moisture, and will sag under heavy weight (the exact weight is based on the dimensions and quality of the hardboard) unless secured to even weight distribution among several mounting points.