Hi,
I have been spending so much time over Israel-Lebanon border, I thought I should write couple of words about.
First of all – this is the only border of All Israel borders that almost had not been changed since Israel independence war (1948). The biggest change was due the conquer of Golan Heights by Israel on the Six Day war (1967), which the eastern part of the border between the countries.
The border line is based on the border set between the British Mandate and the area controlled by French on the Middle East (which split the Middle East between them on Sykes–Picot Agreement (1916)) and was set on the Paulet–Newcombe Agreement (1923).
During part of the time the border was considered the “Good Fence”, for it was a quiet open border and allowed Christian Lebanese to enter Israel.
Apart from the independence war, there were several wars between Israel and Lebanon and part of time (1985-2000) Israel army has set inside Lebanon (the occupied belt). during this time The real border was several km north to the real border.
After 2000, when Israel withdraw from the occupied belt, the border was set as the blue line by the UN. Hezbollah keeps calming there are 14 points along the border (including Ghajar) where Israel still helds Lebanon territories.
Now, the settlements along the border are empty and it is mainly the army that sits around the border. Which means the real border is several km south of the Blue Line.
Take Care
Gad
The railway tunnel Rosh Hanikra, used now as a visitor center of the site. The black curtain is the Israeli – Lebanon border 
on the most west point of it.
Israel-Lebanon border from the Israeli side on Metula.
Egel Gate (Source: Amud Anan) near Metula
The border fence on Galilee panhandle
The border road going over Ghajar bridge (the border itself in this location is the Hasbani stream itself
The border fence between The Roman bridge over the Hasbani stream and Ghajar
The most eastern part of the border between Israel and Lebanon is on Mount Hermon. The part we call Mount Dov in still on argument between Israel and Lebanon and one of the 14 locations Hezbollah claims need to be returned to Lebanon