Robe for a Hat

As graduation comes near, I've been inundated with offers to buy a frame for my diploma, a huge mug with my name on it (the official name of this item escapes me now), graduation announcements and of course, graduation apparel. However, my knitting abilities and passion come through once again, and I make a trade with a wonderful friend (and luckily, a former law student). My friend Annie is lending me her graduation apparel, and in return, I've offered my knitting services to create her a hat. I'm sitting at the drawing board, sending her ideas - what kind of yarn, what color yarn, what style of a hat, etc. So, ideas for a hat - please come my way!!