The affix in comes after the verb kṛ when the objects in composition with it are the words stamba 'a sheaf' and śakṛt 'ordure'.,
Thus स्तम्ब + कृ + इन् = स्तम्बकरि nom. sing. स्तम्बकरिः; so also शकृत्करिः.
Var:- This rule is applicable when the sense of the words to be formed, is that of 'rice' and 'a calf' respectively. Therefore स्तम्बकरिः means 'rice', and शकृत्करिः, 'a calf'.
When the words have not the senses of 'rice' and 'a calf', the affix अण् is employed. As स्तम्बकारः 'sheaf-maker', शकृत्कारः 'ordure-maker'.,