Concertina doors are doors that fold at the bottom to form a single panel or section. They are commonly referred to as bi-fold doors, although they usually have more than one panel. The term concertina is derived from the musical instrument of the very similar name. These types of doors also come in many different styles and sizes; some of which you will probably be familiar with, such as those found on office buildings, cars and houses, and others that you may not. Concertina Accordion Folding Door There are many different designs of these doors. The most popular ones are those that have large panels and are made of wood. They can also be made of metal, or glass, or even some combination of all three materials. Other designs feature a single panel, or two, and the other panels can be covered in fabric. You can also get the door with no panels at all. Different companies produce these doors. They all use different types of materials, so it can be difficult to choose the best one for your requirements. Some of these companies also offer installation services, and the prices can vary from company to company. However, if you are unsure whether you would like to do this yourself, then you may want to choose a company that does. This will ensure that the company does all the work.