While most guitars come with the standard tuners, you may be on
the fence as to whether you want to switch to a more versatile tuner
known as a ‘locking tuner’ Of course, adding locking tuners means that
you’ll need to make a slight modification to your headstock, although
this relatively easy to do yourself, or to get somebody else to do it,
which will involve drilling holes into your guitar!
http://www.askaudiomag.com/locking-tuner/