This is the ideograph for a walled corner pitch with the dimensions two Indus units by two Indus units. An extra line has been added which divides the corner in two. Hence, this symbol is the
noun half corner pitch.
Sample Text Reference:
Mohenjo-daro: Seal: M-119 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 41: Collections in India: Suomalainen Tiedeakatemia.