The affix aṇ comes in the sense of 'what bears it' after the word śakaṭa being in Accusative -2nd case construction.,
Thus शकटं वहति = शाकटः 'an ox' i. e. what bears a car. This could be evolved by तस्येदम् अण् as शाकटस्य वोढ = शाकटः ॥ The specification indicates that tadanta-vidhi applies here, as द्वे शकटे वहति = द्वैशकटः, and the affix is not elided 4.1.88.,