You can snap to a poly edge. Just make sure the cursor is on the edge you want to snap to before you press the MMB. Otherwise you'll be waiting forever for that little guy to jump over to the edge you want. You may be able to adjust the snapping tolerance but it should work fine with the default.
Dave
Edit: Keef answered while I was typing ... spooky!
Last edited by swankymonkey; 20-07-2005 at 11:50 AM.