Mugs-aligning images properly - is there a gizmo?

[GoldRapt]

Hi All,
I always have trouble aligning graphics onto mugs so that they are straight vertically and horizontally.
I do it by eye and sometimes I get wonky
So I was wondering how everyone else applied theirs, is there a tool that does it for you or is it just the luck of the draw for you as it is for me?

[John G]

I print trim lines out with the image, cut to the trim lines and line up with the bottom or top of the mug - if the mugs are straight this works.

Cheers john

[GoldRapt]

Thanks for that John, had not thought of using the top or bottom edges with trim lines.