An affix -- prāgdīvyato'ṇ [[4.1.83]] etc. comes after a word in the Accusative -2nd case in construction in the sense of 'a door which looks towards that'.,
Thus स्रौघ्नः 'a gate which looks towards Srughna', -- as a gate of Kanyakubja. So also माथुरम्, राष्ट्रियम् ॥
Objection. The sutra would have stood better as अभिनिष्क्रमणं द्वारं, for by using अभिनिष्क्रामति, you make the word द्वारं as if it was a being endowed with sense.
Ans. This objection may be answered by saying that the gate is the well-known instrument (करण) to the action of अभिनिष्क्रमण; and an instrument may be used as an agent to a verb: as साध्वसिश्छिनत्ति 'the sword cuts nicely.'
Why do we say द्वारम् \when it is a gate\? Observe स्रुघ्नमभिनिष्क्रामति पुरुषः 'a person faces towards Srughna'.,