Question

What do you use a pastry wheel for?​

Answer 1

to cut dough & to cut other yeasty things of that sort.

Answer 2

You use a pastry wheel to cut dough. It's similar to a pizza knife, but can come in a variety of shapes (e.g. to make a wavy cut) and doesn't have to be as sharp (might be beneficial to have a blunt-ish pastry wheel to preserve the pastry board, depending on material.