The Indus Dictionary Project
This is a pictograph of a wooden staircase viewed in profile. The spaces between the newels and the spindles depict four steps. It is therefore, the noun staircase.
Lohumjo-daro: Seal: Lh-1 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 357: Collections in India: Suomalainen Tiedeakatemia.
Indus Script Sign Number 2225: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.