Everyone has answered your question but just some food for though, when you get to where you have sheeted wings like are on most wings these days on the leading edge, then you can find an article in the May 2005 issue of MA starting on page 46 you can find a very good way to patch wings (or anything else for that matter) where you have sheeting.

I had a mishap with my Funtana, and used this technique for the first time, and was very impressed with the results. You used cross-grain thin cuts of balsa and CA them down under the hole on the sides and that acts like a shelf. Then you cut a balsa square, or whatever you shape you cut where the hole was, and then just shape to fit.

I love this method, and have found it very great to use on sheeted planes. But on my trainer, I just use a patch of the same covering and do like has already been stated.

Hope this helps

~Michael~