It does not mount internal storage, and it will not work if your device doesn't have External Memory Card Support..
UMS Enabler (Universal) v1.6.2.apk
(can also be downloaded from XDA Labs)
(click here for older versions of app)
Steps to Enable UMS:
1. Connect phone using USB cable to Computer or TV or DVD/Audio Player or Mac (or even to other phone with OTG) or whatever.
2. Open the 'UMS Enabler' app and press 'Enable Mass Storage' and give it root access.
(Try 2-3 times if it doesn't work the first time itself)
3. Before disconnecting USB, eject from Computer and then press 'Disconnect Mass Storage' in app.
If it doesn't work, go to App Settings and choose the required settings, and try again.
Avoid using memory card from phone when in UMS mode..
This will work only if there is USB Gadget support in your kernel..
(Not required if you don't make changes in memory card from computer, that is, if you're just using for read-only purpose.)
And remount similarly after use.
Testers, please try and reply.
If it works, please leave a reply with your device model & ROM (and custom kernel if any) in which it's working so that I can make a list of working devices.
Hit the Thanks button if it worked for you..
@vikasb32 (Material Design)
@maais (Russian Localization)
@WormsWarII (French Localization)
Latest Version: 1.6.2
Last Release Date: 2017-02-26
Last Updated 2017-02-26
Source Code: https://github.com/GokulNC/USB_Mass_Storage_Enabler
(Feel free to contribute)