I call the trim around a cushion or pillow cording. It is also called piping or welt. It is the stuff that trims upholstery and slipcovers to give a finished professional look.
When I make a cushion cover I custom make the cording although it may be bought at a fabric store in limited fabrics and colors.
To start I purchase cord in 6/32″ thickness. This will be covered in the fabric of the project or can be made to contrast, however contrasting welt must be sewn more carefully to give a nicely finished effect.
The fabric that encases the cord should be cut on the bias to ease the turning of corners and other non-straight situations (like scallops). When I need miles and miles of piping for a project I follow these instructions to cut the bias tape.
With the zipper foot on the sewing machine I stitch the bias binding onto the cord wrong sides together.
The excess fabric will ultimately be caught up in the seams of the cushion cover.
This is the bit that has been holding me up. Now I can actually get started on the cover itself.
Jo