In this pictograph, posts are set in the ground forming an obstacle. Hence, it is an ideograph for the noun barrier.
Illustrative Text References:
Harappa: Seal: H-271 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 256 (The reference number suggests India, but the location is Pakistan. Hence, it was omitted from Volume 1.): Collections in Pakistan: Suomalainen Tiedeakatemia.
Mohenjo-daro: Seal: M-1203 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 145: Collections in Pakistan: Suomalainen Tiedeakatemia.
Image Credit:
Indus Script Sign Number 189: Sign List of the Indus Script: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.