A "yarn guide"? It's one of those thimble things with pegs and a snap-cover, presumably designed to keep pesky yarn under control when doing one-handed colorwork. I found it to be more hassle than otherwise, but you may be of a different opinion.
Send me a couple of stamps and it's yours...
+++++++++++++Reply to the list as I do not publish an email address to USENET. This practice has cut my spam by more than 95%. Of course, I did have to abandon a perfectly good email account...