Not my idea, I think it was from one of Tim McCreight's many books,

To quickly identify your silver solder, make a different shaped bend in each one.

Mine has one bend (L Shape) for Extra Easy, two bends (U Shape) for Easy, three bends (square) for Medium, which just leaves Hard which is wider than the rest (6mm) and Enamelling which is thin and nearly square section anyway (1 mm x 1.5 mm)

This picture explains it better