Font Book is an application programme which became part of Mac OS X as of version 10.3 "Panther". It is a massive improvement on Mac OS X dealing with fonts (see Fonts in Mac OS X). Font collections can be created, edited and removed by using Font Book. Using Font Book, single or multiple fonts or font collections can be activated or disabled. Beginning with Mac OS X 10.3, double-clicking a font file opens Font Book automatically. With a single click, it is then possible to install the font into the system. Font Book is located within the Applications folder on the Mac OS X startup drive.