This is a pictograph of a gate, which has been deliberately set at an angle by the artist. Adjacent to the gate is a lifting device. The gate can be raised or lowered. Hence, it can be determined
that this Indus symbol is a pictograph of a flow gate.
Illustrative Text Reference:
Lothal: Seal: L-86 a: Jagat Pati Joshi and Asko Parpola, 1987: Corpus of Indus Seals and Inscriptions: Volume 1: Page 258: Collections in India: Suomalainen Tiedeakatemia.
There is only one extant example of this Indus sign.
This gate was probably used to control the level of water in the tidal dock at Lothal.