One thing you experience in life, is that when you buy tools of any kind, buy quality and buy it one time...unless you're careless and tend to lose things. The type of chain tools you buy at a big box store, hardware store or even some bike shops, aren't the best quality like a Park Chain Tool or other name brands. Yeah you'll pay a few bucks more, but it will be in your tool box, ready to go for years to come. Read up on chain measurement for a bike system, and the installation of the chain at the Park Bike Maintenance link or check out Sheldon Brown's instructions for any bike repair or adjustments. Read about what you're about to do so you have an idea of how to proceed with the job.