अपाच्चतुष्पाच्छकुनिष्वालेखने

Operational rule vidhi

The augment सुट् is placed before क , when the verb कृ comes after अप and the sense is 'the scraping of earth by four-footed animals or birds'.

Word by word (padaccheda)

Left context अपात् pañcamī · ekavacanaRight context चतुष्पात्- शकुनिषु saptamī · bahuvacanaRight context आलेखने saptamī · ekavacana

Left context Pañcamī (5th case): "after X", the operation applies to what follows (1.1.67 तस्मादित्युत्तरस्य). Also used for limits and sources.
Right context Saptamī (7th case): "when X follows", the operation applies to what precedes (1.1.66 तस्मिन्निति निर्दिष्टे पूर्वस्य). Also a condition or domain ("in the sense of").

Full reading

अपात् चतुष्पात्-शकुनिषु आलेखने

Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.

Commentary

The augment सुट् is placed before क , when the verb कृ comes after अप and the sense is 'the scraping of earth by four-footed animals or birds'.
Thus अपस्किरते वृषभो हृष्टः, अपस्किरते कुक्कुटो भक्ष्यार्थी; अपस्किरते श्वा आश्रयार्थी = आलिख्य विक्षिपति ॥ Why do we say 'four-footed animals or birds'? Observe अपकिरति देवदत्तः ॥

Vart:- This rule applies when the scraping is through pleasure, or for the sake of finding food, or making a resting place. Therefore not here:- अपकिरति श्वा ओदनपिण्डमाशितः ॥ And it is in the above senses of scraping through pleasure &c, that the root takes Atmanepada affixes; otherwise the Parasmaipada affixes will follow. See 1.3.21. Vartika

Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.