The material generally used in slojd-teaching, and most suitable for the purpose, is wood or timber.

Intelligent knowledge of the material used is as essential to the teacher as acquaintance with the tools required. He ought, e.g., to be familiar with the qualities which render different kinds of wood more or less appropriate for different purposes. Accordingly the description of the tools given in Chapter III (Tools). is here preceded by a brief account of the growth of trees; of the most important properties of wood, and the principal changes which it undergoes; and by a comparison of the technical qualities of the various kinds of wood in common use.