In “Educational sloyd,” as devised by Otto Salomon in the 1870s, woodworking projects were designed to build incrementally on the child’s growing skill. This was accomplished by making the projects grow in degree of difficulty over a period of time, through the introduction of complexity of shape and procedures and through the gradual introduction of more difficult woodworking tools. Salomon believed that the teacher should carefully study and know each child. It was said that from the student’s perspective, no project should be any more difficult than the immediately preceding project. Sloyd was taught through the use of series of models, growing in difficulty and complexity that the students were supposed to accurately reproduce without interference from the teacher. Salomon developed "exercises" in the use of various tools leading to proficiency in the making of models. The exercises in the use of various tools were developed through careful study by Salomon, but he also encouraged that model series be adapted and made relevant to the various cultures in which sloyd was taught. The objects in the model series were designed to be useful to the child and his family, thereby building a relationship of good will and mutual support in the child's education.