Mounting sconces on a mirror takes a bit of skill and coordination. The glass/mirror installer typically cuts the mirror to exact specifications so the electrician can install the fixtures. I hope that helps. Hire a professional if you need help.
The sconces can be adjusted as necessary. We put a French Glaze on the cabinetry in all of the baths and in the Kitchen to get a bit of relief from all the wood finishes. Hand carved mirrors with an ebony finish add depth and a touch of glamor to the vanities. The wall lamps can be adjusted for