Sandcarved signs and plaques can be mounted by drilling holes through the glass and using metal standoffs to mount the glass to a wall. When using standoffs, it’s important to have the holes drilled to accommodate the diameter of the standoffs. The size of the standoffs is directly related to the weight of the glass piece to be mounted.
You will have to supply a template for the glass fabrication as to where the holes need to be drilled. Then, it is important to match the holes of the glass with the possible metal backdrop you are going to have fabricated; the holes of both objects have to match up since the standoffs will have to pass through both in order to attach them to the wall.
—Ruth Dobbins, EtchMaster