You are wearing this nice gown or blouse, each time you keep tucking back your bra strap to hide it from view, but it keeps coming out.
This clever clothing trick not only keeps your bra strap concealed but also keeps your wide neck shirts from falling off your shoulder. All it takes are a few thin strips of fabric and sew-on press studs.
Attach one end of the fabric with one stud under the sleeve/strap of the cloth as shown in the pic, then sew the another stud to the other of the fabric. Adjust it to tighten properly.