Im not confident in my ability to explain this but I will try . Many hundreds of years ago , maybe even also thousands, I don't know , when they built castles with turrets and tall towers , they built staircases in a very specific way . They were spirals and very narrow , so narrow that people going up or down had to do so in single file . This was for defence purposes . They also built them so that if u were going up the staircase it wound clockwise , this effectively blocked your right hand because there was so little room on the right hand as that was where the centre of the corkscrew / spiral was . If u were coming down it was the complete opposite . The spiral was tight on your left hand but , u had plenty of room on the right hand in order to draw your sword and defend the building . So , towers and turrets etc , were hard to attack and take from the bottom and easy to defend from the top . The actual steps u were stood on were elongated triangles , the narrow pointed angle was very narrow on the right for those coming up ( attacking ) and the wide flat side was nice and roomy on the right for those coming down ( defending ) . Hope all that was understandable .