If you're buying nails, you should know that there are two types -- common nails and finish nails. Common nails have large flat heads and are for rough work. Finish nails are thin and can be driven below the surface with a nail set. The indentation then can be filled in with putty. Nails are sized by the "penny" system, a number and a small letter "D." You can gauge how long a nail is by dividing penny size by four and adding a half-inch. Thus, an 8-penny nail would be (eight divided by four) two (plus one-half inch). Two-and-one-half inches long. To always get the best price, buy in bulk instead of those expensive little packages. And that's the On The House tip for today.