The Manta Ray squat support is on the surface a pretty simple device. It is a piece of molded plastic in the shape of, well, a Manta Ray. It has a groove through the middle that clips onto the bar, and wings that spread out over your back and shoulders for support and stabilization. It is both incredibly simple to use, and highly effective.
To use it, you simply clip it onto the bar via a grove in the mold - see pictures. This puts the bar in an ideal position, and spreads the weight over a wider area across your back and shoulders thereby making the lift far more comfortable. Then you step underneath and rest it across your back.
One of the very best exercises for doing developing explosive strength in your jumping muscles is the squat. Unfortunately many people avoid doing this great exercise for a number of reasons. The Manta Ray is such terrific value because it removes some of the biggest issues people have with squatting.