This app is for systems with root access only. It offers 3 main functions:
Apply selected TTF fonts to the system
Backup system fonts to /sdcard/Fonts
Restore backed up fonts from /sdcard/Fonts
Place any TTF files you have in /sdcard/Fonts for easiest access.
In order for Android to reload its system fonts, the system must be rebooted after applying. Also, most ROM updates will overwrite your fonts with the default ones while installing. To easily restore, simply find a set of fonts that work well for you and then select Backup fonts so that you can restore them later. Be aware that this simply overwrites any existing backup you have, so you may want to save the original fonts elsewhere if you think you may need them.