The highly fissile slate shows the highest bending strength among all stones. Due to its cleavage plane it is possible to split slate into 2–3 mm thin shingles. This distinct property makes slate especially suitable for roofing and cladding. This chapter gives a brief overview of the different roofing styles and specific slate works such as pattern, ornaments or pictures which are often made with slate of different colours. Slate is a building material used since prehistoric time by men and literally applied for the same different architectonical purposes as other dimension stones. Slate often does not attract particular attention in architecture compared to other dimension stones like sandstone, marble or granite except in the slate districts themselves. Hence, the chapter shows the wide variety of the architectonical usage of slate. The international trade has been accelerated in the last two decades and this globalisation means for slate that producers of the main slate districts somehow dominate the slate market while other vanish. The chapter shows the economic importance of slate as dimension stone and describes the fact that dimension stones are traded with commercial names and are often assigned with inappropriate terms in respect to the stone type.