I mentioned this in the first garden tips competition as a means of protecting your vegetable patch.
As the drawing above shows, a simple plant protection structure can be made out of inexpensive materials. The three-hoop system is simply made out of heavy duty plastic water piping - be sure that the gauge you by is flexible enough for the job. It is usually bought in rolls. The cross bar along the top is linked with a length of wire running through it that is wrapped around each of the side hoops. It is best to use two separate pieces of tubing along the top of the hoops, one adjoining the left hand hoop to the center, and another joining the right hand hoop to the center. The hoops don't even need to be attached to the beds themselves - I merely push mine into the soil to the depth of about 6 inches. This makes them easy to remove whenever you are working on the beds.
The type of covering you put over the top of the hoops is up to you. Bird netting will keep the birds and other pests off, such as possums, but a finer netting will even keep cabbage moth off your brassicas. A word of warning on finer netting - if growing vegetables that require pollination, a wider netting gauge is preferred as you don't want to stop the pollinators from getting in.
The dots along the side of the beds are nails that are driven into the beds to act as hooks for the netting you drape over.
The beauty of this system is that you can make the hoops as tall or as short as you need for what ever plants you are growing. I have separate covers that I rotate between beds depending on what I'm growing. For instance, I have a hoop cover that is only about 3 foot high for the root crop bed, but I have another hoop cover that is 6 foot high for vegetables such as tomato and climbing beans that need more height.
Cheers,
John
you could see them trying to work it out but hooray they couldn't. 
