Finish checking are those little hairline cracks that you see in the finish on many older guitars. A guitar that is 30 years or older can develop these merely from the finish drying out and aging. The environment that the guitar spends its life in is also a contributing factor. Some players like myself find these tiny hairline cracks to add character to and instrument and also a certain “relic” look. But what about the player that purchases a new guitar and wants to keep it looking new and does not like that “checked” relic look? One easy preventative measure is to keep your guitar from going form one extreme temperature to another. For example let’s say that you just finished with your gig or jam session in the middle of winter and it is below freezing outdoors. You pack up your guitar and amp and put it in your car and head for home. On the drive your guitar can get very cold even if it is in the case and in a heated car. When you arrive home you should wait until the case and the guitar comes to room temperature before opening the case. The same applies to a guitar you just received in the mail during the cold winter months. If you open your guitar case immediately you run the risk of having your guitar literally check in front of your eyes. I have personally witnessed this on a really nice Gretsch Country Classic reissue. The guitar spent the entire day in a trunk of athe owners car during the cold month of January. It was then opened immediatley in a warm room and checked right on the spot! It can happen that fast. This is a method some guitar builders use to achieve that checked “relic” look on a brand new guitar. What actually happens is the wood of the guitar warms and expands faster than the finish. Due to this expansion the finish cracks. So always be patient and wait to open a cold guitar case or that boxed up ebay purchase that spent the day in a cold delivery van. It could save the finish of your guitar.