Before finishing your entry door system, you must know whether your entry door panel and sidelights are fiberglass or steel. If you're unsure if your entry door is made of fiberglass or steel, place a magnet on your door — if it sticks, it's most likely steel.Your Pella packaging and sales invoice should also indicate the door type. Check with your Pella representative for specific information on your product. Visit the Pella Help Library for finishing tips.