Final answer:
A medium-grit abrasive is used for initial shaping of the perimeter of the nail.
Step-by-step explanation:
A medium-grit abrasive is used for initial shaping of the perimeter of the nail. This is because the medium-grit abrasive provides enough roughness to remove excess length and shape the nail, but is not too coarse to cause damage or discomfort to the nail bed or surrounding skin. The medium-grit abrasive allows for a controlled and precise shaping process.