Fibre cement sheet is the most prominant and common form of asbestos that people recognise as being potentially hazardous. True fibre cement sheet is a very hard material. Caution should be applied in determining whether the sheet material is cement or insulating board. insulating board is a softer material and releases fibres much more readily than the stronger cement counterpart. An good indication of true asbestos cement is a golf ball or dimpled pattern on the back of the sheet. Asbestos insulating board will generally have a smoother finish to the back. The first picture below is of an external wall made of fibro and the second picture is of ceiling and wall lining which are most common in internal wet areas.