Bas relief showing medieval stone masons at work circa 1408. Starting from the left the first mason is building a wall, the second holds a drill whilst working on a column, the third uses a compass and a square to build a capital whilst the fourth is sculpting a putti with a mattock. Masons? tools are shown hanging on the wall behind. They include a square, a straight-edge, a compass and a plumb-rule.This is part of a sculpture of ?quattro coronati? or four saints by Nanno de Banco commissioned by the Wood and Stonemasons Guild for the church of Orsanmichele in Florence