The Indus Dictionary Project
This is a pictograph of a door or gate. The Indus symbol for a door or a gate is always two Indus units wide. This one is three Indus units tall.
Lothal: Seal: L-88 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 259: Collections in India: Suomalainen Tiedeakatemia.
The shape of the symbol suggests that the people of the Indus Civilisation may have used mortise and tenon joinery in construction.
Indus Script Sign Number 2072: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.