Just in the reverse of the mullion appears a kneeling figure, with its right hand on the chest and holding a cartouche with the left hand where, according to the tradition, it was writing “architectus”. This image represents Master Mateo himself, who places himself looking at the high altar, offering his work to Santiago. Traditionally, faithful people hit the sculpture’s head against themselves three times so that Master Mateo could transfer some of his wisdom to them, and for that reason, it is known as Santo dos croques.