I have a pair of leica binoculars model 102...

You are correct that the lines are for rangefinding. This is what is called a reticle. Without seeing how they are set up it is hard to determine the scale used. Most scales are in meters, some in yards, but they all work the same. Go to any of the following websites and download the instruction manual.
Go to Tasco and search for the Offshore OS 36 or 54 manual. OR go to Steiner Optic and download the manual for the Military 7x50 or Commander or Navigator models.
These instruction manuals have details and diagrams of how to read a rangefinder reticle.
Basically if you know the distance to an object you can estimate its height or size. OR if you know the size of an object you can estimate the distance to the object.