This is a useful technique for sewing vinyls. Such as marine vinyl or other vinyl types that get a deep crease when sewn normally.
In fursuit costume construction, this technique is very useful for creating rounded noses, rounded or shaped paw pads, big claws that are rounded, and other features that are intended to have a smooth curve.

This technique makes any deep crevices or darts in your project smoothed out and lay flat. While also adding a handsome final touch.

Left un-treated. Right topstitched with this technique!

This is how the back side of the project looks.
I hope you enjoy this technique! Thank you so much for subscribing to my patreon! :D