This foot guides your topstitching and edge stitching perfectly.  The bottom of the foot is stepped, so that the thicker portion of the fabric goes on the left and the thinner part goes on the right.

For 7mm machines, including:

3160QDC, 4120QDC, 5300QDC,  Sewist 721, Sewist 725, Sewist 740DC, Sewist 780DC, Skyline S3, Skyline S3 AE