The use of technology to support mathematics goes back to ancient tally sticks, khipus, counting boards, and abacuses. The reciprocal relationship, the use of mathematics to support technology, also has a long history. Preliterate weavers, most of them women, combined geometrical and arithmetical thinking to construct number series that give rise to intricate symmetrical patterns on the cloth. Egyptian scribes performed the technical calculations needed for large building projects. Islamic master builders covered walls and ceilings with complex geometric patterns, constructed with advanced ruler-and-compass methods. In Europe, medieval masons used the same tools to construct intricate geometrical patterns for instance in rose windows. These masters lacked formal mathematical schooling, but they developed advanced skills in constructive geometry. Even today, the practical mathematics of the crafts is often based on traditions that differ from school mathematics.