Scaleboard (or sca'board) is a thin board most often split from blocks of wood with a metal froe. In European bookbinding, sca'boards were most often obtained from beech, whose fine, straight grain made it most suitable for this purpose. It differs from the thicker, cleft planks also obtained by splitting timber in that it is much thinner, ranging from approximately 3mm down to less than 1mm. At such thicknesses, the wood is easily broken and it was therefore sometimes laminated to or between pieces of paper board. It was used most often on small-format books in cheap bindings, such as school books and inexpensive devotional literature from at least the mid-sixteenth century. It was seen to be an inferior quality material, presumably on account of its brittleness, and attempts were made in England in the sixteenth century to prevent its use. It was in much more common use in Germany, but was used to varying extents in all western-European countries. In an apparent contradiction of preferred practice, some binders, most notably in New England, but also in Germany, used sca'boards with a horizontal grain, to reduce the likelihood of the boards breaking along the grain by having one end-grain edge of each board braced against the joint of the bookblock.
Bernard Middleton, A history of English Craft Bookbinding Techniques, New Castle, London, Oak Knoll Press, The British Library, 1994 (4th ed.)
Michael Felix Suarez and H. R. Woudhuysen, eds (2010), The Oxford Companion to the Book, 2 vols, Oxford, Oxford University Press.