The affix ṭhak comes in the sense of 'what bears it' after the words 1. hala and 2. sīra in Accusative -2nd case construction.,
Thus हलं वहति = हालिकः a ploughman सैरिकः 'a plough ox.' The ठक् would have come by 4.3.124, the specification shows tadantavidhi and non-elision, as द्वैहालिकः, त्रैसीरिकः ॥,