Border wire is a 9 gauge wire used on the front edge of a sprung chair or sofa. The alternative is to use a heavy cane also available. Border wire/cane clips are also available to save lashing the springs on with twine.
Border Wire is approx 3mtr length
Click here for Border Cane approx. 2m
Click here for Border wire clips
NB Picture is taken from the Practical Upholstering Book by Frederick Palmer