Quick Tip #7: Easy Proportion Guide
For beginners and, for that matter, some advance tiers have problems in getting the right proportions for the flies they are tying. By placing on a clip, the 
same size hook for the fly you are tying, you have a very simple and accurate gauge for measuring. When a pattern calls for a tail equal to body length, tie in the tail material and then measure it against the hook you have in the clip. So easy, it almost feels like cheating.