This is a pictograph of an alcove or bay, which would have been used for storage.
Illustrative Text Reference:
Mohenjo-daro: Incised Copper Tablet: M-1486 A: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 208: Collections in Pakistan: Suomalainen Tiedeakatemia.
Comment:
This is Mahadevan's sign number 1005, which I have redrawn to better reflect the original.
Image Credit:
Alcove: Lynn Fawcett, 2020.