If ready made piping cord is not available or if you just want to make your own, the piping foot is ideal for the job. The piping foot (sometimes mistakenly reffered to as the cording foot) is designed with two grooves on the underside and will holod and cover the cord when making piping tape. It can also be used for attaching piping.
Maximum cord size 5mm. For larger cord size see 'Adjustable Zipper Foot'.