Arbalestina
The narrow cruciform loophole, called by architects ' Arbalestina,' which is usually to be seen in the masonry of a mediaeval fortress, was designed for the special use of crossbowmen in repelling an assault. To enable the crossbow, or longbow, to be aimed to the right or left through a loophole, the aperture was greatly widened out on the inside face of the perforated wall.