This Indus symbol is comprised of two door leaves. The leaf on the right is set in the open position. Hence, Mahadevan's sign number 2125 depicts an open door. It can be likened to the Chinese character mǎo 𢨯.
Illustrative Text Reference:
Mohenjo-daro: Seal: M-678 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 35: Collections in Pakistan: Suomalainen Tiedeakatemia.
Comment:
In the context of inscription M-678, it seems likely that mahadevan's sign number 2125 should be read as the verb to welcome or to receive.
Image Credit:
Indus Script Sign Number 2125: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.