Have you finished reading the 211 page manual for the Sony NEX-7 yet? You may have run into this Dial / Wheel Lock option in the Setup Menu and tried to guess what it was. We had no clue until we ran into the video above by SonyAlphaSupport.
The Dial / Wheel Lock option can be found on the 1st screen (top) of the Setup Menu. It can be set to All, Control Wheel, or Off. When it is set to All, the Tri-Navi controls can be locked by holding down the Navigation Button of the NEX-7 for around 2 seconds. This means that whatever the Tri-Navi controls are controlling cannot be accidentally changed without unlocking them. The unlocking process is the same as the locking process.
A more useful option might be setting the Dial / Wheel Lock to Control Wheel. The Control Wheel is usually the ISO dial so it can be locked and unlocked by holding down the Navigation Button for around 2 seconds.
Dial / Wheel Lock option in NEX-7 Setup Menu
A lock icon shows up on the top right of the screen when the Dial / Wheel Lock is activated. It blinks orange when the dials are moved while they are locked.
Navigation Button located next to NEX-7 Shutter Button
To date we have had no issues of accidentally changing our settings by inadvertent movement of the Tri-Navi dials but this is a good option to have.