I thought this was a great video about adjusting the backstay.  In case you were wondering what the backstay is, it is a piece of standing rigging that runs from the transom to the top of the mast.  On many boats this piece of equipment can be adjusted while sailing.  If you have hung out at Sailnet's forum you will find the author involved in many conversations and is well respected.  This is a nice basic overview of tensioning the backstay and how this affects the handling of a sailboat.

You should come away from this video with the following points:

• identify where the backstay is located
• how this affects the shape of the mast and sail
• when you might want to add tension to the backstay