After a few years of continued use you may find your key no longer slots into the cylinder lock as smoothly as it once did. This how to video shows a simple trick that will fix sticking door locks using nothing more than a pencil, sharp knife, a piece of paper and the key itself.

Once ready, simply scrape some of the pencil lead into shavings onto the piece of paper, you will need to do this for a minute or two to create a pile of lead shavings as shown in the video. 

Next sprinkle the shavings over the key making sure it settles in the grooves, then push the key in and out of the door lock a few times. You will find the key should now slide into the cylinder easily.

This method of lubricating your door locks is also good practice as part of the routine maintenance of your doors and door furniture.