Measure all four edges of your mirror using a measuring tape. Make sure that the measurements are as accurate as possible.
Cut four pieces of pre-finished wood molding of appropriate lengths using a circular saw. If you have a very tall mirror, you may need to cut two pieces of wood molding for the mirror’s height.
Cut each end of each strip of wood molding to a 45-degree angle. The result should be four lengths of wood molding that fit together like a picture frame. If you needed two strips for one side, they serve as one strip, and therefore, only one end of each side strip should be beveled.
Apply a thin layer of mirror adhesive to the back of one of the wood molding strips.
Fit the wood molding strip to the mirror’s matching edge and hold it there for several seconds.
Glue the other strips to the mirror in similar fashion and allow the glue to cure completely. The amount of time necessary for the glue to cure is recorded on the glue’s label. When the glue cures, the mirror is ready for regular use.