The h with cross and semicircle symbolizes Ihesus "gate of the Heaven" in the first half of the twelfth century. In the second half it symbolizes a crossbow, weapon to protect the temple.
The crossbow appeared in the tenth century and spread throughout Europe. At the beginning was despised by the aristocracy for going against the close combat. The Church and the Empire tried to ban it, for this reason it appears belatedly in the Romanesque transforming a sign similar but with other meaning.
San Isidoro de León, Catedral de Santiago de Compostela, Santa María de la Oliva (Navarra), Santa María de Monsalud (Guadalajara), Santes Creus (Tarragona), San Juan de Portomarín (Lugo).
Read more in The stonemason’s signs in the Romanesque churches in Spain.