Installing the clips for a frameless mirror seems like an easy enough task -- and it is -- but it's also easy to mess up if you don't make accurate measurements. If you neglect this part of the job, your mirror may hang askew or the clips may be distributed asymmetrically around the mirror. It's also important to use anchors strong enough to support your mirror.
About Those Anchors
Your package of plastic mirror clips or metal J-clips might come with conical plastic anchors for installation in drywall. These types of anchors are rated only for light loads; if your mirror weighs more than about 10 pounds, consider supporting it with winged plastic anchors or -- if it is very heavy -- toggle bolts.
You install one of these anchors by drilling a pilot hole large enough for it to fit through -- it latches onto the back of the drywall and is virtually impossible to remove without breaking the drywall.
Installing Clips for a Rectangular Mirror
Measure the length and width of the mirror, using a tape measure, and measure the area of the wall to ensure you have enough space for the mirror.
Determine where the center point of the mirror will be from the walls or features on either side and make a light mark within 4 feet of the floor, using a pencil. This will be where the bottom of the mirror goes.
Place a 2-foot level on the mark; extend it to the floor and center the bubble to make the level vertical. Make another light mark along the line defined by the level to denote the bottom edge of the mirror.
Put the level on the second mark and center the bubble to make it horizontal. Measure the distance from one side of the mark to the corner of the mirror, and make a third mark to denote the position of one of the bottom clips. Make a mark for the other bottom clip on the other side of the center point.
Drill pilot holes for the anchors to support the two bottom clips; install the anchors, and screw the clips loosely to the anchors. The clips should be secure enough to support the mirror.
Place the mirror temporarily in the bottom clips. Center it, and make two marks on the top edge for the other pair of clips. Use a tape measure to ensure that the clips are same distance from the mirror edges as the bottom ones.
Remove the mirror; install the anchors for the top clips. Then set the mirror back in position, and install the top clips. Tighten all four clips to hold the mirror securely, using a screwdriver.
Installing Clips for a Circular or Oval Mirror
Installing the clips for a non-rectangular mirror symmetrically calls for a bit of mathematical know-how. You can do this with masking tape, which is easy to remove after you've mounted the mirror.
To distribute the clips for a circular mirror symmetrically, you need to define four equidistant points on the perimeter -- do this by laying a piece of masking tape on the glass that extends across the mirror, then laying another one at a 90-degree angle to the first one; measure the angle with a carpenter's square. Mark the center point of the edge of each piece of tape, and then hold the mirror on the wall and use those marks to make four other marks on the wall to denote the positions of the clips. You can then install the clips and hang the mirror.
Use a tape measure to find the maximum distance along the long axis of the oval, and lay tape across the face of the mirror between these two points. Choose a point from 1 to 6 inches from the top edge of the mirror -- depending on the size of the mirror. Mark that point on the tape, and lay another piece of tape perpendicularly to the mirror edges. Repeat the procedure on the bottom edge.
Set the mirror against the wall, and use a level to make the long piece of tape vertical. Make marks for the clips at the centers of the four short pieces of tape that intersect the edges.