Hey Kelly. The wheeled nippers will cut a straight line across a fairly narrow strip of glass, say up to maybe two inches, SOMETIMES. (Sometimes they make a curved break. You just have to live with it, and practice helps, but some glass is just gonna break in a curve no matter what you do.) Make sure first that the wheels are tight (they should have come with an allen wrench). The wheels should not wiggle or turn. Basically you place your glass between the wheels so the wheels will meet near the edge of the glass, with the wheels in line with where you want your break to go. Hold your glass in one hand, the nippers in the other, and squeeze til it breaks. If you need me to, I can post photos of it "in action" :)

Oh, I just realized, I am so used to using them for stained glass, that's what I was talking about above. You can also use them to nip away at china or tiles to get the shape you want. You can use them to break a plate in half (more or less) using them like I described in my first post. I couldn't do what I do without them.

Excellent tutorial HERE.