The affix cha (īya) comes in the same sense of 'that whose purpose is this' after the word samāpana when it has a word in composition preceding it.,
This debars ठञ् ॥ Thus छन्दः समापनं प्रयोजनमस्य = छन्दः समापनीयम्, व्याकरण समापनीयम् ॥ The specific mention of the word पद in the aphorism indicates that the rule will not apply when a word other than a 'pada,' such as the affix 'bahuch,' (V. 3. 68.) precedes the word Samapana.,