This design was quite simply nothing more than a walkway (from the French "Patrol Walk"). Incorporated into castle designs around the 12th/13th Century, these walkways allowed archers or other "missile troops" to safety attack approaching enemy. They also allowed Guarding troops to have some element of safety as they patrolled "the walls". They were often accessed by stairways (made of wood or stone). There were even examples of portable Chemin de Ronde's that could be rolled up to older Castles.