The Indus Dictionary Project
This is a pictograph of a boundary marker, which has been divided by a line down the centre. Hence, it is the noun border.
Mohenjo-daro: Seal: M-1316 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 168: Collections in Pakistan: Suomalainen Tiedeakatemia.
In inscription M-1316, the border symbol is scaled to roughly half character height, and it is centred in the character area.
Border: Lynn Fawcett, 2019.