This is a part of the mosquito net.
Mosquito nets are insect repellent nets that were used all over Japan in the past.
 
In mid-summer, it was so hot that we used to open all the windows in the house and sleep surrounded by mosquito nets.
 
Several places have been repaired by sashiko stitching. 

Material: indigo and turmeric dyed ramie

Mesures: 146cm×133cm (57in × 52in)