Most of Japanese houses have sliding shutter doors by windows. A sliding shutter door is very important and it protects people from storms like a typhoon, a tornado, a strong wind, and thieves trying to break in a house. It’s also used as an insulater.
A sliding shutter door is made light woods, right iron plates, and aluminum plates, etc (We don’t see wood sliding shutter doors much anymore though). They are strong enough to protect the house from calamities. And people can lock then only from inside of the house, so it’s difficult for thieves to break in from outside.
All sliding shutter doors are used to be opened/closed by hand, but now there are many automatic sliding shutter doors.