A mirror has four pieces of hardware of the one appearing in the image, one at each corner.
Attempting to insert simultaneously four flat-head wood screws in these slots would likely be frustrating. Plus I'd rather leave myself some room for not getting the locations of the screws so absolutely accurate.
Is there some hardware that matches the one pictured? Would two screws be enough or, if four are present, four are necessary? Is this mirror meant to be hung as shown, or rotated 90 degrees? Are these pieces of hardware meant for somehow adding a cable, then hanging the mirror from that cable? Would the cable need to go around all four, perhaps loosely to distribute the load?
Best Answer
This is a part of a security hanger set:
Security Hanger Set
Two of the straps you have pictured go on the top of the mirror, and the clips on the right side of the picture go on the wall and hook into the straps.
One strap is installed in the bottom center of the mirror and the T-shaped screw in the center of the picture gets installed in the wall horizontally. The mirror is hung and the T screw fits perfectly in the horizontal slot of the strap. Then the wrench at the bottom of the picture is used to rotate the T-screw vertically to lock it into the strap.
If you only have one on the bottom of the mirror, chances are something else was used along the sides or top to hang it and the bottom strap was used only for the security T-screw. Or the straps at the top were removed by someone to be used on another hanging.