Instead, take advantage of your lens hood and put your lens right up against the fence. The lens hood will prevent the glass element from getting scratched, and your lens will be close enough to the fence that it will focus right through it. Be sure to line the lens up with one of the diamond-shaped gaps.
If you are not using a SLR with a telephoto lens, then the lens on your point and shoot camera will likely be small enough to actually fit through the gaps in the fence.
You can get some pretty amazing shots this way. For instance, in baseball and softball games, I will line up behind home plate and get a lot of great shots of the pitcher going through their complete windup and pitch. I have also shot batters and catchers this way.
All of these were shot through the fence.
Try it and you'll see -- it's not as hard as you think!

