July 18, 2013, 02:42:59 am
Hi M3.0
You are using the correct method, Context Menu --> Transformation --> Lock Position --> Lock.
If it is moving down then it might not be locked, please check that the object icon you are selecting is for the required model, and then the Lock Position is On.
For terrain, that's also preferred, to lower the terrain so rest of areas start with the base terrain at 0 height