Snap hangers are used to attach wire to the back of metal frames. The advantage of the snap hanger is that it is easily adjusted. If you are hanging a show of 20 pictures the same size and you want them to all be aligned this would be the easiest way to do so. Rather than changing the picture hook in the wall to adjust the height of the picture, you could merely press down on the snap hanger and move it up or down in the channel. This is not recommended for heavier pictures because it can "slip" and lacks the strength of the standard omni hanger. Position the hanger approximately 1/3 down from the top of the frame and snap into the channel. The hanger can be repositioned by pressing down with your thumb and sliding it up or down in the channel.