 Opus gallicum

The opus gallicum (Latin for "Gallic work") was a technique of construction whereby precise holes were created in stone masonry for the insertion of wooden beams to create a wooden infrastructure.The technique was so named because, though its presence is attested in protohistoric times, its use was common enough in Gaul to merit mention in Julius Caesar's "De bello Gallico" and was frequently employed in the Merovingian era.