Metal roofing comes in many pieces that need to be precisely manufactured or it might cause delays during installation. When you order this material, you need to make sure that all the quantities and dimensions are precise. Do not just give the field measurements to the manufacturer and assume they will send you the correct pieces. The number of pieces, which piece goes where need to be verified and the manufacturer will need you to give you a labeled drawing, otherwise your installer will have a very hard time in the field installing this.