"Molly had that elephantgrey dress with the braided frogs. Mantailored with selfcovered buttons." (U8.163)
From Wikipedia: A frog is an ornamental braiding for fastening the front of a garment that consists of a button and a loop through which it passes. The purpose of frogs is to provide a closure for a garment while decorating it at the same time. They are usually used on garments that appear oriental in design. Frogs are usually meant to be a design detail that "stands out".
Many sewers make their own because supplies are inexpensive and the results are customizable. Self-fabric can be used to create frogs that are the same color as the garment, though frogs are usually chosen to be a contrasting color to that of the garment.