This stitch, as the name suggests, is two rows of chevron stitches mirroring each other. Infinite rows of this stitch can be created to make beautiful fillings with effect. Try using different colors for each row or shades of the same color for different effects. 

You need to know the chevron stitch to be able to do this stitch. 

 mirrored_chevron_ stitch_1        mirrored_chevron_stitch_2
Fig 1: Start by doing a row of chevron stitch. Then, start doing another row of chevron stitch below the first. Only, this time, it begins inverted, as shown.    Fig 2: All the points of the top row and the bottom row would coincide, as you can see. This creates the ‘mirrored’ effect. 
 mirrored_chevron_stitch_3   Fig 3: A portion of the two rows looks like this.