Klaf or Qelaf is the designation given a particular piece of skin. The Talmudic definition includes both the form of the skin and the way it is processed, in particular, that it must be tanned. Since the innovative ruling of Rabbeinu Tam it is primarily used to refer to parchment or vellum. It is one of the materials upon which a sofer writes certain Jewish liturgical and ritual documents.
Klaf - a parchment with an ink and quill
Parchment is a writing material made from specially prepared untanned skins of animals—primarily sheep, calves, and goats. It has been used as a writing medium for over two millennia. Vellum is a finer quality parchment made from the skins of young animals such as lambs and young calves.
Central European (Northern) type of finished parchment made of goatskin stretched on a wooden frame
Parchment with a quill and ink
Latin grant dated 1329, written on fine parchment or vellum, with seal
A 1385 copy of the Sachsenspiegel, a German legal code, written on parchment with straps and clasps on the binding