Springald

The springald is a medieval torsion siege engine that threw bolts using twisted skeins of silk or sinew to power two inward swinging bow arms, working on the same principle as the ancient Greek or Roman ballista. Its earliest reference appears in France in 1249, and it was documented in England by 1266, most often mounted on towers and gates as a defensive weapon. By 1382 springalds were being phased out in favor of crossbows and firearms, though some Germanic and Swiss regions kept using them into the early fifteenth century.