key band
/ˈkiː band/noun
1Originally: a band of leather, fabric, metal, etc., for carrying keys and keeping them together. Later chiefly: a band or strap holding the key for a locker at a swimming pool, sports centre, etc., typically worn round the wrist or ankle.
2 Art and Architecture. A band or strip of key pattern forming a decorative border; a fret or meander.
Origin
Late Middle English. From key + band.