Once empowered to erect a mission in a given area, the men assigned to it chose a specific site that featured a good water supply, plenty of wood for fires and building material, and ample fields for grazing herds and raising crops. The Fathers blessed the site, and with the aid of their military escort fashioned temporary shelters out of tree limbs roofed with thatch, reeds, or in Pimería Alta saguaro ribs or ocotillo branches topped with brush and mud. These simple huts would ultimately give way to the stone and adobe buildings that exist today.